PUBLICATIONS
2024
Most neuroeconomic research seeks to understand how value influences decision-making. The influence of reward type is less well understood. We used functional magnetic resonance imaging (fMRI) to investigate delay-discounting of primary (i.e., food) and secondary rewards (i.e., money) in 28 healthy, normal-weighted participants (mean age = 26.77; 18 females). To decipher differences in discounting behavior between reward types, we compared how well different option-based statistical models and attribute-wise heuristic choice models captured the reward-specific discounting behavior. Contrarily to our hypothesis of different strategies for different rewards, we observed comparable discounting behavior for money and food (i.e., exponential discounting). Higher k values for food discounting suggest that individuals decide more impulsively if confronted with food. fMRI revealed that money discounting was associated with enhanced activity in the right dorsolateral prefrontal cortex, involved in executive control, the right dorsal striatum, associated with reward processing, and left hippocampus, involved in memory encoding/retrieval. Food-discounting, instead, was associated with higher activity in left temporo-parietal junction suggesting social reinforcement of food decisions. Although our findings do not confirm our hypothesis of different discounting strategies for different reward types, they are in line with the notion that reward types have a significant influence on impulsivity with primary rewards leading to more impulsive choices.
Aphantasia prohibits people from experiencing visual imagery. While most of us can readily recall decade-old personal experiences (autobiographical memories, AM) with vivid mental images, there is a dearth of information about whether the loss of visual imagery in aphantasics affects their AM retrieval. The hippocampus is thought to be a crucial hub in a brain-wide network underlying AM. One important question is whether this network, especially the connectivity of the hippocampus, is altered in aphantasia. In the current study, we tested 14 congenital aphantasics and 16 demographically matched controls in an AM fMRI task to investigate how key brain regions (i.e., hippocampus and visual-perceptual cortices) interact with each other during AM re-experiencing. All participants were interviewed regarding their autobiographical memory to examine their episodic and semantic recall of specific events. Aphantasics reported more difficulties in recalling AM, were less confident about their memories, and described less internal and emotional details than controls. Neurally, aphantasics displayed decreased hippocampal and increased visual-perceptual cortex activation during AM retrieval compared to controls. In addition, controls showed strong negative functional connectivity between the hippocampus and the visual cortex during AM and resting-state functional connectivity between these two brain structures predicted better visualization skills. Our results indicate that visual mental imagery is essential for detail-rich, vivid AM, and that this type of cognitive function is supported by the functional connection between the hippocampus and the visual-perceptual cortex.
Introduction: Loneliness poses a significant health problem and existing psychological interventions have shown only limited positive effects on loneliness. Based on preliminary evidence for impaired oxytocin signaling in trait-like loneliness, the current proof-of-concept study used a randomized, double-blind, placebo-controlled design to probe intranasal oxytocin (OT) as an adjunct to a short-term modular-based group intervention for individuals suffering from high trait-like loneliness (HL, UCLA loneliness scale ≥ 55).
Methods: Seventy-eight healthy HL adults (56 women) received five weekly group psychotherapy sessions. HL participants received OT or placebo before the intervention sessions. Primary outcomes were trait-like loneliness measured at baseline, after the intervention, and again at two follow-up time points (three weeks and three months), and, assessed at each session, state loneliness (visual analog scale), perceived stress (Perceived Stress Scale, PSS-10), quality of life (World Health Organization Five Well-Being Index, WHO-5), and the therapeutic relationship (Group Questionnaire, GQ-D).
Results: The psychological intervention was associated with significantly reduced perceived stress and improved trait-like loneliness across treatment groups, which was still evident at the 3-month follow-up. OT had no significant effect on trait-like loneliness, quality of life, or perceived stress. However, compared to placebo, OT significantly facilitated the decrease in state loneliness within sessions and significantly improved positive bonding between the group members.
Conclusion: Despite significantly improved trait-like loneliness after the intervention, OT did not significantly augment this effect. Further studies are needed to determine optimal intervention designs to translate the observed acute effects of OT into long-term benefits.
2023
Individual differences in delay discounting—how much we discount future compared to immediate rewards—are associated with general life outcomes, psychopathology, and obesity. Here, we use machine learning on fMRI activity during an intertemporal choice task to develop a functional brain marker of these individual differences in human adults. Training and cross-validating the marker in one dataset (Study 1, N = 110 male adults) resulted in a significant prediction–outcome correlation (r = 0.49), generalized to predict individual differences in a completely independent dataset (Study 2: N = 145 male and female adults, r = 0.45), and predicted discounting several weeks later. Out-of-sample responses of the functional brain marker, but not discounting behavior itself, differed significantly between overweight and lean individuals in both studies, and predicted fasting-state blood levels of insulin, c-peptide, and leptin in Study 1. Significant predictive weights of the marker were found in cingulate, insula, and frontoparietal areas, among others, suggesting an interplay among regions associated with valuation, conflict processing, and cognitive control. This new functional brain marker is a step toward a generalizable brain model of individual differences in delay discounting. Future studies can evaluate it as a potential transdiagnostic marker of altered decision-making in different clinical and developmental populations.
Abstract
Schizophrenia is associated with various deficits in social cognition that remain relatively unaltered by antipsychotic treatment. While faulty glutamate signaling has been associated with general cognitive deficits as well as negative symptoms of schizophrenia, no direct link between manipulation of glutamate signaling and deficits in mentalizing has been demonstrated thus far. Here, we experimentally investigated whether ketamine, an uncompetitive N-methyl-D-aspartate receptor antagonist known to induce psychotomimetic effects, influences mentalizing and its neural correlates. In a randomized, placebo-controlled between-subjects experiment, we intravenously administered ketamine or placebo to healthy participants performing a video-based social cognition task during functional magnetic resonance imaging. Psychotomimetic effects of ketamine were assessed using the Positive and Negative Syndrome Scale. Compared to placebo, ketamine led to significantly more psychotic symptoms and reduced mentalizing performance (more “no mentalizing” errors). Ketamine also influenced blood oxygen level dependent (BOLD) response during mentalizing compared to placebo. Specifically, ketamine increased BOLD in right posterior superior temporal sulcus (pSTS) and increased connectivity between pSTS and anterior precuneus. These increases may reflect a dysfunctional shift of attention induced by ketamine that leads to mentalizing deficits. Our findings show that a psychotomimetic dose of ketamine impairs mentalizing and influences its neural correlates, a result compatible with the notion that deficient glutamate signaling may contribute to deficits in mentalizing in schizophrenia. The results also support efforts to seek novel psychopharmacological treatments for psychosis and schizophrenia targeting glutamatergic transmission.
Novel and reformulated food, in particular protein-enhanced drinks, provide an important strategy to promote healthy eating. Despite their availability, protein-enriched foods are not widely accepted, likely owing to their unexpected “taste”. Those expectations change with experience and exposure may improve product acceptance. However, the sensory drivers of this phenomenon are unknown. In this randomised, controlled, multi-center trial with pre and post intervention measurements, 100 healthy adult participants consumed either a novel protein-enriched milk drink (PD) or a conventional milk drink (CD) for seven days. Participants evaluated familiarity and hedonic value of the taste, smell, and flavor of different milk drinks including the intervention drinks in the laboratory before and after a seven day exposure. A novel protein-enhanced drink was evaluated after intervention only. Exposure to PD increased familiarity of its smell, taste, and especially flavor. The perception of the other non-exposed drinks was unchanged. PD exposure also led to increased taste familiarity of a novel protein drink suggesting that the “acquired taste” transfers to other protein drinks. While PD hedonic ratings were unaffected by exposure, increased familiarity was positively associated with hedonic ratings for all three sensory modalities smell, taste, and flavor. No changes in the perception of any drink were observed in the group consuming the CD. The transfer of the acquired taste familiarity to a novel drink after 7-days of exposure to an unfamiliar protein-enriched drink indicates that exposure may increase acceptance of similar drinks.
2022
Introduction: Nutrition claims are one of the most common tools used to improve food decisions. Previous research has shown that nutrition claims impact expectations, however, their effects on food perception, valuation, and their neural correlates are not well understood. These claims may have both intended and unintended effects on food perception and valuation, which may compromise their effect on food decisions. Methods: We investigated the effects of nutrition claims on expectations, perceptions, and valuation of milk-mix drinks in a behavioral (n = 110) and an fMRI (n = 39) study. In the behavioral study, we assessed the effects of a “fat-reduced” and a “protein-rich” nutrition claim on expected and perceived food attributes of otherwise equal food products. In the fMRI study, we investigated the effect of a “protein-rich” claim on taste pleasantness perception and valuation, and on their neural correlates during tasting and swallowing. Results: We found that both nutrition claims increased expected and perceived healthiness and decreased expected but not perceived taste pleasantness. The “protein-rich” claim increased expected but not perceived satiating quality ratings, while the “fat-reduced” claim decreased both expected and perceived satiating quality ratings. In the absence vs. presence of the “protein-rich” claim, we observed an increased activity in a cluster extending to the left nucleus accumbens during tasting and an increased functional connectivity between this cluster and a cluster in middle frontal gyrus during swallowing. Conclusion: Altogether, we found that nutrition claims impacted expectations and attenuated reward-related responses during tasting but did not negatively affect perceived pleasantness. Our findings support highlighting the presence of nutrients with positive associations and exposure to foods with nutrition claims to increase acceptance. Our study offers insights that may be valuable in designing and optimizing the use of nutrition claims.
Many intertemporal trade-offs are unbalanced: while the advantages of options are concentrated in a few periods, the disadvantages are dispersed over numerous periods. We provide novel experimental evidence for “concentration bias,” the tendency to overweight advantages that are concentrated in time. Subjects commit to too much overtime work that is dispersed over multiple days in exchange for a bonus that is concentrated in time: concentration bias increases subjects’ willingness to work by 22.4% beyond what standard discounting models could account for. In additional conditions and a complementary experiment involving monetary payments, we study the mechanisms behind concentration bias and demonstrate the robustness of our findings.
To survive, all animals need to predict what other agents are going to do next. We review neural mechanisms involved in the steps required for this ability. The first step is to determine whether an object is an agent, and if so, how sophisticated it is. This involves brain regions carrying representations of animate agents. The movements of the agent can then be anticipated in the short term based solely on physical constraints. In the longer term, taking into account the agent’s goals and intentions is useful. Observing goal directed behaviour activates the neural action observation network, and predicting future goal directed behaviour is helped by the observer’s own action generating mechanisms. Intentions are critically important in determining actions when interacting with other agents, as several intentions can lie behind an action. Here, interpretation is helped by prior beliefs about the agent and the brain’s mentalising system is engaged. Biologically-constrained computational models of action recognition exist, but equivalent models for understanding intentional agents remain to be developed.
Recent advances in the neuropsychopharmacology of metacognition indicate a constituent role of glutamate for the integrity of metamnestic processes. However, the extent to which previous results can be generalized across functional domains to characterize the relationship between glutamate and metacognition remains unclear. Here, in a randomized, double-blind, placebo-controlled, preregistered fMRI study, we tested the effects of a psychotomimetic dose (target plasma concentration 100 ng/mL) of the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist ketamine on metacognition in a perceptual decision-making framework. We collected trial-by-trial metacognitive reports as participants performed a two-alternative forced-choice perceptual task during functional magnetic resonance imaging (fMRI). Results indicated ketamine-induced deterioration in metacognitive performance, whereas no significant effects were observed for perceptual performance, response times and – unexpectedly – metacognitive bias. Whilst there were no detectable ketamine effects on mean BOLD activation, exploratory psychophysiological interaction (PPI) analysis revealed alterations in functional connectivity during metacognitive confidence ratings under ketamine. Specifically, there was increased task-specific connectivity for ketamine compared to placebo between right anterior dorsolateral prefrontal cortex and left middle temporal, supramarginal and precentral gyrus, as well as between right insula/inferior frontal gyrus and left lingual gyrus, possibly indicating re-representations of object-level features supplied for metacognitive evaluations. Overall, these findings contribute towards the emerging picture of the substructures underlying metacognitive operations at the neurotransmitter level and may shed light on a neural pattern characteristic of pharmacologically challenged metacognition.
Background: Loneliness is a public health concern with detrimental effects on physical and mental well-being. Given phenotypical overlaps between loneliness and social anxiety, cognitive behavioral interventions targeting social anxiety might be adopted to reduce loneliness. However, it is still elusive whether social anxiety and loneliness share the same underlying neurocognitive mechanisms. The current study aimed at investigating to what extent known behavioral and neural correlates of social avoidance in social anxiety are evident in loneliness.
Methods: We used a pre-stratified approach involving 42 participants with high and 40 control participants with low loneliness scores. During functional magnetic resonance imaging, the participants completed a social gambling task to measure the subjective value of engaging in a social situation and responses to positive and negative social feedback.
Results: Uni- and multivariate analyses of behavioral and neural data replicated known task effects across groups. However, although lonely participants were characterized by increased social anxiety, loneliness was associated with a response pattern clearly distinct from social anxiety. Specifically, Bayesian analyses revealed moderate evidence for equal subjective values of engaging in social situations and comparable amygdala responses to social decision-making and striatal responses to positive social feedback in both groups. Conversely, lonely participants showed significantly altered behavioral responsiveness to negative feedback and reduced striatal activity, whereas striatal-hippocampal connectivity was increased compared to controls.
Conclusion: Our findings suggest that loneliness is associated with altered emotional reactivity to social situations rather than behavioral tendencies to withdraw from social interactions. Thus, established interventions for social anxiety should be adjusted when targeting loneliness.
Social cognition and metacognition are frequently impaired in schizophrenia, and these impairments complicate recovery. Recent work suggests that different aspects of metacognition may not be impaired to the same degree. Furthermore, metacognition and the cognitive capacity being monitored need not be similarly impaired. Here, we assessed performance in detecting cues of intentional behaviour as well as metacognition about detecting those cues in schizophrenia. Thirty patients and controls categorized animations of moving dots into those displaying a dyadic interaction demonstrating a chase or no chase and indicated their confidence in these judgments. Perception and metacognition were assessed using signal detection theoretic measures, which were analysed using frequentist and Bayesian statistics. Patients showed a deficit compared to controls in detecting intentionality cues, but showed preserved metacognitive performance into this task. Our study reveals a selective deficit in the perception of intentionality cues, but preserved metacognitive insight into the validity of this perception. It thus appears that impairment of metacognition in schizophrenia varies across cognitive domains - metacognition should not be considered a monolithic stone that is either impaired or unimpaired.
2021
Information has a long history of being used with the intention to influence people's behavior, particularly in situations where people are likely to condition their own behavior on what they expect most others to do. We experimentally study how selective (favorable or unfavorable) information about past cooperativeness of unrelated groups affects cooperation in problems of collective action. We find cooperation to crucially depend on pre-play information, coinciding with a change in initial beliefs. In addition, we find unfavorable information to substantially reduce the effectiveness of peer punishment. This prevents groups that start off on the wrong foot from recovering over time. The impact of information does not rely on information being public or private. Yet it critically relies on the information being surprising. In a cooperative environment, it is unfavorable information that matters; in an uncooperative environment, it is favorable information.
Burgeoning evidence indicates that women are more sensitive to the context of an offer and show a stronger propensity to adjust their behavior with changing fairness frames. We evaluated whether the sex hormone estradiol and associated stereotypical beliefs contribute to fairness framings by administering topical estradiol (2 mg) to 108 healthy women and 104 heathy men in a randomized, double-blind, placebo-controlled between-subject study design. Participants played the role of the responder in a modified version of the Ultimatum Game (UG), in which identical offers for the division of a given amount of money were framed as either fair or unfair. Furthermore, participants completed an unframed UG and a delayed discounting task to probe possible effects of estradiol on altruistic preferences and delay gratification. Our results show that women were more sensitive to fairness frames than men. Intriguingly, however, estradiol had sex-specific effects on fairness sensitivity by increasing the acceptance rate of proposals with a fair frame in men and reducing it in women. Furthermore, the mere belief of receiving estradiol treatment significantly increased the acceptance of unfair-framed offers in both sexes, but estradiol did not significantly alter the response to unframed offers and impulsive decision-making. Collectively, our findings indicate that estradiol has opposing effects on the sensitivity to the perceived fairness of economic offers in women and men. The profound effects of estradiol treatment and stereotypical beliefs provide support for the notion that sex differences in fairness framing are rooted in both biological and environmental factors.
Intertemporal choice involves deciding between smaller, sooner and larger, later rewards. People tend to prefer smaller rewards that are available earlier to larger rewards available later, a phenomenon referred to as temporal or delay discounting. Despite its ubiquity in human and non-human animals, temporal discounting is subject to considerable individual differences. Here, we provide a critical narrative review of this literature and make suggestions for future work. We conclude that temporal discounting is associated with key socio-economic and health-related variables. Regarding personality, large-scale studies have found steeper temporal discounting to be associated with higher levels of self-reported impulsivity and extraversion; however, effect sizes are small. Temporal discounting correlates negatively with future-oriented cognitive styles and inhibitory control, again with small effect sizes. There are consistent associations between steeper temporal discounting and lower intelligence, with effect sizes exceeding those of personality or cognitive variables, although socio-demographic moderator variables may play a role. Neuroimaging evidence of brain structural and functional correlates is not yet consistent, neither with regard to areas nor directions of effects. Finally, following early candidate gene studies, recent Genome Wide Association Study (GWAS) approaches have revealed the molecular genetic architecture of temporal discounting to be more complex than initially thought. Overall, the study of individual differences in temporal discounting is a maturing field that has produced some replicable findings. Effect sizes are small-to-medium, necessitating future hypothesis-driven work that prioritizes large samples with adequate power calculations. More research is also needed regarding the neural origins of individual differences in temporal discounting as well as the mediating neural mechanisms of associations of temporal discounting with personality and cognitive variables.
Only little research has been conducted on the pharmacological underpinnings of metacognition. Here, we tested the modulatory effects of a single intravenous dose (100 ng/ml) of the N-methyl-D-aspartate-glutamate-receptor antagonist ketamine, a compound known to induce altered states of consciousness, on metacognition and its neural correlates. Fifty-three young, healthy adults completed two study phases of an episodic memory task involving both encoding and retrieval in a double-blind, placebo-controlled fMRI study. Trial-by-trial confidence ratings were collected during retrieval. Effects on the subjective state of consciousness were assessed using the 5D-ASC questionnaire. Confirming that the drug elicited a psychedelic state, there were effects of ketamine on all 5D-ASC scales. Acute ketamine administration during retrieval had deleterious effects on metacognitive sensitivity (meta-d') and led to larger metacognitive bias, with retrieval performance (d') and reaction times remaining unaffected. However, there was no ketamine effect on metacognitive efficiency (meta-d'/d'). Measures of the BOLD signal revealed that ketamine compared to placebo elicited higher activation of posterior cortical brain areas, including superior and inferior parietal lobe, calcarine gyrus, and lingual gyrus, albeit not specific to metacognitive confidence ratings. Ketamine administered during encoding did not significantly affect performance or brain activation. Overall, our findings suggest that ketamine impacts metacognition, leading to significantly larger metacognitive bias and deterioration of metacognitive sensitivity as well as unspecific activation increases in posterior hot zone areas of the neural correlates of consciousness.
Social cognition and metacognition are frequently impaired in schizophrenia, and these impairments complicate recovery. Recent work suggests that different aspects of metacognition may not be impaired to the same degree. Furthermore, metacognition and the cognitive capacity being monitored need not be similarly impaired. Here, we assessed performance in detecting cues of intentional behaviour as well as metacognition about detecting those cues in schizophrenia. Thirty patients and controls categorized animations of moving dots into those displaying a dyadic interaction demonstrating a chase or no chase and indicated their confidence in these judgments. Perception and metacognition were assessed using signal detection theoretic measures, which were analysed using frequentist and Bayesian statistics. Patients showed a deficit compared to controls in detecting intentionality cues, but showed preserved metacognitive performance into this task. Our study reveals a selective deficit in the perception of intentionality cues, but preserved metacognitive insight into the validity of this perception. It thus appears that impairment of metacognition in schizophrenia varies across cognitive domains - metacognition should not be considered a monolithic stone that is either impaired or unimpaired.
Everyday dietary decisions have important short-term and long-term consequences for health and well-being. How do we decide what to eat, and what physiological and neurobiological systems are involved in those decisions? Here, we integrate findings from thus-far separate literatures: (a) the cognitive neuroscience of dietary decision-making, and (b) growing evidence of gut–brain interactions and especially influences of the gut microbiome on diet and health outcomes. We review findings that suggest that dietary decisions and food consumption influence nutrient sensing, homeostatic signaling in the gut, and the composition of the gut microbiome. In turn, the microbiome can influence host health and behavior. Through reward signaling pathways, the microbiome could potentially affect food and drink decisions. Such bidirectional links between gut microbiome and the brain systems underlying dietary decision-making may lead to self-reinforcing feedback loops that determine long-term dietary patterns, body mass, and health outcomes.
Background
During the COVID-19 pandemic people started stocking up on daily necessities although no long-term shortage thereof could be expected. Among other variables such as perceived and desired control, experienced scarcity, and psychopathy, obsessive-compulsiveness has been proposed as plausible explanation for this seemingly irrational behavior.
Methods
We collected data of 1379 participants in an online survey. Buying behavior during the COVID-19 pandemic was measured with the Hamsterkauf Questionnaire (HQ), which was specifically developed for this purpose. As independent variables, we measured participants’ obsessive-compulsiveness on the Dimensional Obsessive-Compulsive Scale (DOCS) and potential fears of incapacitation and destabilization it might fuel. We also determined the extent to which participants experienced scarcity, exhibited psychopathic traits, felt in control of the situation and desired control in general.
Results
The average DOCS score was found to be strongly elevated. Higher obsessive-compulsiveness was associated with stronger stockpile purchasing behavior. This association was partly mediated by fears of incapacitation and destabilization. Obsessive-compulsiveness was predicted by experienced scarcity and psychopathic personality traits. By contrast, desirability of control and perceived control were not significantly associated with obsessive-compulsiveness or panic buying behavior.
Limitations
Survey data were collected in form of a convenience sample at one measurement point.
Conclusions
The widespread stockpile purchasing behavior during the COVID-19 pandemic can partly be understood as safety behavior to reduce fears related to strongly elevated levels of obsessive-compulsiveness. In turn, elevated levels of obsessive-compulsiveness were partly accounted for by personality factors such a psychopathy and situational stress factors such as scarcity.
2020
Motor function after hemispheric lesions has been associated with the structural integrity of either the pyramidal tract (PT) or alternate motor fibers (aMF). In this study, we aimed to differentially characterize the roles of PT and aMF in motor compensation by relating diffusion-tensor-imaging-derived parameters of white matter microstructure to measures of proximal and distal motor function in patients after hemispherotomy. Twenty-five patients (13 women; mean age: 21.1 years) after hemispherotomy (at mean age: 12.4 years) underwent Diffusion Tensor Imaging and evaluation of motor function using the Fugl-Meyer Assessment and the index finger tapping test. Regression analyses revealed that fractional anisotropy of the PT explained (p = 0.050) distal motor function including finger tapping rate (p = 0.027), whereas fractional anisotropy of aMF originating in the contralesional cortex and crossing to the ipsilesional hemisphere in the pons explained proximal motor function (p = 0.001). Age at surgery was found to be the only clinical variable to explain motor function (p < 0.001). Our results are indicative of complementary roles of the PT and of aMF in motor compensation of hemispherotomy mediating distal and proximal motor compensation of the upper limb, respectively.
Simulations of neural networks can be used to study the direct effect of internal or external changes on brain dynamics. However, some changes are not immediate but occur on the timescale of weeks, months, or years. Examples include effects of strokes, surgical tissue removal, or traumatic brain injury but also gradual changes during brain development. Simulating network activity over a long time, even for a small number of nodes, is a computational challenge. Here, we model a coupled network of human brain regions with a modified Wilson-Cowan model representing dynamics for each region and with synaptic plasticity adjusting connection weights within and between regions. Using strategies ranging from different models for plasticity, vectorization and a different differential equation solver setup, we achieved one second runtime for one second biological time.
Human decisions are often influenced by emotions. An economically relevant example is the role of fear in generating loss aversion. Previous research implicates the amygdala as a key brain structure in the experience of fear and loss aversion. The neural mechanism behind emotional influences on loss aversion is, however, unclear. To address this, we measured brain activation with functional magnetic resonance imaging (fMRI) while participants made decisions about monetary gambles after viewing fearful or neutral faces. We observed that loss aversion following the presentation of neutral faces was mainly predicted by greater deactivations for prospective losses (relative to activations for prospective gains) in several brain regions, including the amygdala. By contrast, increases in loss aversion following the presentation of fearful faces were mainly predicted by greater activations for prospective losses. These findings suggest a fear-induced shift from positive to negative value coding that reflects a context-dependent involvement of distinct valuation processes.
Computational studies of the influence of different network parameters on the dynamic and topological network effects of brain stimulation can enhance our understanding of different outcomes between individuals. In this study, a brain stimulation session along with the subsequent post-stimulation brain activity is simulated for a period of one day using a network of modified Wilson-Cowan oscillators coupled according to diffusion imaging based structural connectivity. We use this computational model to examine how differences in the inter-region connectivity and the excitability of stimulated regions at the time of stimulation can affect post-stimulation behaviours. Our findings indicate that the initial inter-region connectivity can heavily affect the changes that stimulation induces in the connectivity of the network. Moreover, differences in the excitability of the stimulated regions seem to lead to different post-stimulation connectivity changes across the model network, including on the internal connectivity of non-stimulated regions.
Norm violations (e.g., unfair transgressions) are often met with punishment even by people who are not directly affected. However, punishing a transgressor is not the only option for a bystander to restore justice. Empathic concerns may dictate instead to give a helping hand to a victim. Using a pre‐registered, fully incentivized eye‐tracking study (N = 47), we investigated the cognitive mechanism linking bystanders’ empathic concern and justice‐restoring intervention behaviour. The results show that not only the decision to intervene (i.e., either costly compensating the victim or punishing the transgressor) but also the attention directed towards a victim’s payoffs (i.e., measured by the proportion of fixations) during the decision‐making period systematically varied with the individual level of empathic concern. Exploring this link further, we additionally instructed participants to focus on specific components of the norm violation, namely the (un)fair conduct of the offender or the victim's feelings. Surprisingly, highly empathic bystanders were more likely to punish the offender when the norm violation was highlighted. However, we did not observe the modulation of the instructed focus on the link between gaze‐based measures and empathic concern. Overall, these results provide initial evidence about the interacting impact of empathic concern as well as the focus on specific components of the norm violation when bystanders respond to unfair transgressions.
Benzodiazepines (BZDs) represent the gold standard of anxiolytic pharmacotherapy; however, their clinical benefit is limited by side effects and addictive potential. Consequently, there is an urgent need to develop novel and safe anxiolytics. The peptide hormone oxytocin (OXT) exhibits anxiolytic-like properties in animals and humans, but whether OXT and BZDs share similar effects on the neural circuitry of fear is unclear. Therefore, the rationale of this ultra-high-field functional MRI (fMRI) study was to test OXT against the clinical comparator lorazepam (LZP) with regard to their neuromodulatory effects on local and network responses to fear-related stimuli. One hundred twenty-eight healthy male participants volunteered in this randomized double-blind, placebo-controlled, between-group study. Before scanning using an emotional face-matching paradigm, participants were randomly administered a single dose of OXT (24 IU), LZP (1 mg), or placebo. On the behavioral level, LZP, but not OXT, caused mild sedation, as evidenced by a 19% increase in reaction times. On the neural level, both OXT and LZP inhibited responses to fearful faces vs. neutral faces within the centromedial amygdala (cmA). In contrast, they had different effects on intra-amygdalar connectivity; OXT strengthened the coupling between the cmA and basolateral amygdala, whereas LZP increased the interplay between the cmA and superficial amygdala. Furthermore, OXT, but not LZP, enhanced the coupling between the cmA and the precuneus and dorsomedial prefrontal cortex. These data implicate inhibition of the cmA as a common denominator of anxiolytic action, with only OXT inducing large-scale connectivity changes of potential therapeutic relevance.
Objective:
Childhood maltreatment is a major risk factor for psychopathology associated with interpersonal problems in adulthood, but the etiological pathways involved are still unclear. The authors propose that childhood maltreatment confers risk for dysfunctional behavior in social interactions by altering interpersonal distance preference and the processing of social touch.
Methods:
Ninety-two medication-free adults (64 of them female) with low, medium, and high levels of childhood maltreatment were tested with an interpersonal distance paradigm and subsequently underwent a social touch functional MRI task during which they rated the perceived comfort of slow touch (C-tactile [CT] optimal speed; 5 cm/s) and fast touch (non-CT-optimal speed; 20 cm/s).
Results:
Participants with high childhood maltreatment levels preferred a larger interpersonal distance and experienced fast touch as less comforting compared with participants with no or moderate childhood maltreatment experiences. On the neural level, participants with severe childhood maltreatment exhibited exaggerated responses to fast touch in the right somatosensory and posterior insular cortex, which correlated with lower comfort ratings. Severe childhood maltreatment was associated with decreased activation in the right hippocampus in response to slow touch. This response pattern was not moderated or mediated by childhood maltreatment–associated region-specific reductions in gray matter volume.
Conclusions:
The study findings suggest that higher childhood maltreatment levels are associated with hypersensitivity characterized by a preference for larger interpersonal distance and discomfort of fast touch. These dysregulations were manifested in a sensory cortical hyperreactivity and limbic CT-related hypoactivation. These results may shed light on why individuals with severe childhood maltreatment exhibit an increased susceptibility to interpersonal dysfunctions and psychiatric disorders in adulthood.
Abstract
Background
While intermittent theta-burst stimulation (iTBS) has been shown to improve symptoms of major depressive disorder (MDD), research has been largely limited to targeting the dorsolateral prefrontal cortex (DLPFC). New approaches utilize patients’ individual resting state fMRI data in order to identify superficial cortical stimulation targets functionally connected to deeper brain regions, thus enabling the modulation of previously inaccessible targets for antidepressant therapy.
Objective
To improve iTBS treatment of MDD by inducing plasticity in the hippocampus through stimulation of an individually mapped, functionally interconnected site in the parietal cortex.
Methods
Fifty-three MDD patients were randomized to three treatment groups and underwent 15 sessions of iTBS to the left DLPFC. This was augmented by adding a second daily session of (i) stimulation over individualized parietal targets functionally connected to the hippocampus, (ii) left DLPFC stimulation, or (iii) sham stimulation. To evaluate the improvement of treatment, we assessed depression severity, neuropsychological performance, functional connectivity and neural activation during an associative memory paradigm pre- vs. post-treatment.
Results
Augmentation of left DLPFC stimulation by parieto-hippocampal stimulation increased functional connectivity between hippocampus and DLPFC as well as encoding-related hippocampal activation; the latter was associated with better performance during a spatial planning task dependent on prefrontal and hippocampal contributions. Depressive symptoms improved in all groups after treatment, with best clinical outcomes following twice-daily left DLPFC stimulation.
Conclusion
Functional connectivity-guided stimulation of the hippocampus may serve as an adjunct to iTBS in order to target the cognitive symptoms of MDD.
A core symptom of schizophrenia is a deficit in social cognition. Furthermore, many patients suffer from relevant social anxiety. How social anxiety relates to social avoidance in schizophrenia is, however, still unclear. To address this question empirically, 30 participants with schizophrenia were compared to individually matched controls in a recently developed experimental task. In each trial, participants chose between a monetary gamble with a human partner providing social feedback and a defined monetary amount that varied across trials. The tendency to avoid the interaction under acceptance of monetary loss served as a measure of social avoidance. Patients showed higher levels of social anxiety assessed using the Liebowitz Social Anxiety Scale (LSAS) than controls, took longer to decide whether to engage in the social interaction and rated social feedback as less intense. Despite making rational decisions, patients surprisingly showed no social avoidance. We assume that the lack of experimentally induced social avoidance in contrast to the well-known social avoidance behavior in everyday life, also reflected by elevated self-rated LSAS scores, was due to a partial compensation of delayed social information processing in the absence of the time constraints in our task. This additional time may have allowed rational decisions and masked potential social avoidance behavior. We conclude that social anxiety in schizophrenia may have different characteristics than in individuals without schizophrenia, namely avoidance of negative feedback caused by prolonged social processing instead of fear of supposed negative feedback. Treatment strategies for social anxiety in schizophrenia may benefit from considering these differences.
Nutrition labels are the most commonly used tools to promote healthy choices. Research has shown that color-coded traffic light (TL) labels are more effective than purely numerical Guideline Daily Amount (GDA) labels at promoting healthy eating. While these effects of TL labels on food choice are hypothesized to rely on attention, how this occurs remains unknown. Based on previous eye-tracking research we hypothesized that TL labels compared to GDA labels will attract more attention, will induce shifts in attention allocation to healthy food items, and will increase the influence of attention to the labels on food choice. To test our hypotheses, we conducted an eye-tracking experiment where participants chose between healthy and unhealthy food items accompanied either by TL or GDA labels. We found that TL labels biased choices towards healthier items because their presence caused participants to allocate more attention to healthy items and less to unhealthy items. Moreover, our data indicated that TL labels were more likely to be looked at, and had a larger effect on choice, despite attracting less dwell time. These results reveal that TL labels increase healthy food choice, relative to GDA labels, by shifting attention and the effects of attention on choice.
Increasing rates of obesity have fueled interest in the factors underlying food choice. While epidemiological studies report that disadvantaged social groups exhibit a higher incidence of obesity, causal evidence for an effect of social contexts on food choice remains scarce. To further our knowledge, we experimentally investigated the effect of disadvantageous social context on food choice in healthy, non-dieting participants. We used three established experimental methods to generate social contexts of different valence in controlled laboratory settings: (i) receiving varying amounts of money in a Dictator Game (DG; n = 40), (ii) being included or excluded in a Cyberball Game (CBG; n = 35), and (iii) performing well, average, or poorly in a response time ranking task (RTR; n = 81). Following exposure to a particular social context, participants made pairwise choices between food items that involved a conflict between perceived taste and health attributes. In line with previous research, stronger dispositional self-control (assessed via a questionnaire) was associated with healthier food choices. As expected, being treated unfairly in the DG, being excluded in the CBG, and performing poorly in the RTR led to negative emotions. However, we did not find an effect of the induced social context on food choice in any of the experiments, even when taking into account individual differences in participants’ responses to the social context. Our results suggest that—at least in controlled laboratory environments—the influence of disadvantageous social contexts on food choice is limited.
Does the pre-treatment profile of individuals with persistent depressive disorder (PDD) moderate their benefit from disorder-specific Cognitive Behavioral System of Psychotherapy (CBASP) versus supportive psychotherapy (SP)? We investigated this question by analyzing data from a multi-center randomized clinical trial comparing the effectiveness of 48 weeks of CBASP to SP in n = 237 patients with early-onset PDD who were not taking antidepressant medication. We statistically developed an optimal composite moderator as a weighted combination of 13 preselected baseline variables and used it for identifying and characterizing subgroups for which CABSP may be preferable to SP or vice versa. We identified two distinct subgroups: 58.65% of the patients had a better treatment outcome with CBASP, while the remaining 41.35% had a better outcome with SP. At baseline, patients responding more favorably to CBASP were more severely depressed and more likely affected by moderate-to-severe childhood trauma including early emotional, physical, or sexual abuse, as well as emotional or physical neglect. In contrast, patients responding more favorably to SP had a higher pre-treatment global and social functioning level, a higher life quality and more often a recurrent illness pattern without complete remission between the episodes. These findings emphasize the relevance of considering pre-treatment characteristics when selecting between disorder-specific CBASP and SP for treating PDD. The practical implementation of this approach would advance personalized medicine for PDD by supporting mental health practitioners in their selection of the most effective psychotherapy for an individual patient.
Several automatic image segmentation methods and few atlas databases exist for analysing structural T1-weighted magnetic resonance brain images. The impact of choosing a combination has not hitherto been described but may bias comparisons across studies. We evaluated two segmentation methods (MAPER and FreeSurfer), using three publicly available atlas databases (Hammers_mith, Desikan-Killiany-Tourville, and MICCAI 2012 Grand Challenge). For each combination of atlas and method, we conducted a leave-one-out cross-comparison to estimate the segmentation accuracy of FreeSurfer and MAPER. We also used each possible combination to segment two datasets of patients with known structural abnormalities (Alzheimer’s disease (AD) and mesial temporal lobe epilepsy with hippocampal sclerosis (HS)) and their matched healthy controls. MAPER was better than FreeSurfer at modelling manual segmentations in the healthy control leave-one-out analyses in two of the three atlas databases, and the Hammers_mith atlas database transferred to new datasets best regardless of segmentation method. Both segmentation methods reliably identified known abnormalities in each patient group. Better separation was seen for FreeSurfer in the AD and left-HS datasets, and for MAPER in the right-HS dataset. We provide detailed quantitative comparisons for multiple anatomical regions, thus enabling researchers to make evidence-based decisions on their choice of atlas and segmentation method.
2019
Agents’ decisions to exert effort depend on the incentives and the potential costs involved. So far, most of the attention has been on the incentive side. However, our laboratory experiments underline that both the incentive and the cost side can be used separately to shape work performance. In our experiment, subjects work on a real-effort slider task. Between treatments, we vary the incentive scheme used for compensating workers. Additionally, by varying the available outside options, we explore the role of implicit costs of effort in determining workers’ performance. We observe that incentive contracts and implicit costs interact in a nontrivial manner. In general, performance decreases as implicit costs increase. Yet the magnitude of the reaction differs across incentive schemes and across the offered outside options, which, in turn, alters estimated output elasticities. In addition, comparisons between incentive schemes crucially depend on the implicit costs.
Against Epilepsy Rasmussen encephalitis (RE) is an immune-mediated brain disease with progressive unihemispheric atrophy. Although it is regarded as a strictly one-sided pathology, volumetric magnetic resonance imaging (MRI) studies have revealed atrophy in the so-called unaffected hemisphere. In contrast to previous studies, we hypothesized that the contralesional hemisphere would show increased gray matter volume in response to the ipsilesional atrophy. We assessed the gray matter volume differences among 21 patients with chronic, late-stage RE and 89 age- and gender-matched healthy controls using voxel-based morphometry. In addition, 11 patients with more than one scan were tested longitudinally. Compared to controls, the contralesional hemisphere of the patients revealed a higher cortical volume but a lower subcortical gray matter volume (all P < 0.001, unpaired t test). Progressive gray matter volume losses in bilateral subcortical gray matter structures were observed (P < 0.05, paired t test). The comparatively higher cortical volume in the contralesional hemisphere can be interpreted as a result of compensatory structural remodeling in response to atrophy of the ipsilesional hemisphere. Contralesional subcortical gray matter volume loss may be due to the pathology or its treatment. Because MRI provides the best marker for determining the progression of RE, an accurate description of its MRI features is clinically relevant.
Age-associated cognitive impairment in general and dementia in particular are a global concern. Preventive lifestyle strategies are highly used but there is a lack of information on the reciprocal relationships between nutrition biomarkers and measures of both cognitive and physical performance. To fill this gap of knowledge, the relationship between plasma levels of the robust nutrition- and antioxidant defense-related biomarkers carotenoid and tocopherols and both indicators of cognitive and physical performance was investigated in a group of persons with mild cognitive impairment participating in the NeuroExercise Study at the German Sport University in Cologne, Germany. In 56 participants with full dataset, significant correlations independently of fruit and vegetable intake were found between plasma levels of β-cryptoxanthin and Timed Up&Go test (p < 0.05), γ-tocopherol and number of daily steps (p < 0.01), as well as between four out of six measured carotenoids—lutein; zeaxanthin; β-cryptoxanthin and β-carotene—and the computerized CogState International Shopping List subtest (p < 0.01). In light of the increasing attention towards the nutritional cognitive neuroscience of carotenoids, computerized measures of cognitive performance might be further implemented in future studies investigating the effects of lifestyle interventions against cognitive and physical impairment.
Objectives The aim of this study was to examine the natural history of brain involvement in adult-onset myotonic dystrophies type 1 and 2 (DM1, DM2). Methods We conducted a longitudinal observational study to examine functional and structural cerebral changes in myotonic dystrophies. We enrolled 16 adult-onset DM1 patients, 16 DM2 patients, and 17 controls. At baseline and after 5.5 ± 0.4 years participants underwent neurological, neuropsychological, and 3T-brain MRI examinations using identical study protocols that included voxel-based morphometry and diffusion tensor imaging. Data were analyzed by (i) group comparisons between patients and controls at baseline and follow-up, and (ii) group comparisons using difference maps (baseline–follow-up in each participant) to focus on disease-related effects over time. Results We found minor neuropsychological deficits with mild progression in DM1 more than DM2. Daytime sleepiness was restricted to DM1, whereas fatigue was present in both disease entities and stable over time. Comparing results of cross-sectional neuroimaging analyses at baseline and follow-up revealed an unchanged pattern of pronounced white matter alterations in DM1. There was mild additional gray matter reduction in DM1 at follow-up. In DM2, white matter reduction was of lesser extent, but there were some additional alterations at follow-up. Gray matter seemed unaffected in DM2. Intriguingly, longitudinal analyses using difference maps and comparing them between patients and controls did not reveal any significant differences of cerebral changes over time between patients and controls. Conclusion The lack of significant disease-related progression of gray and white matter involvement over a period of five years in our cohort of DM1 and DM2 patients suggests either a rather slowly progressive process or even a stable course of cerebral changes in middle-aged adult-onset patients. Being the first longitudinal neuroimaging trial in DM1 and DM2, this study provides useful additional information regarding the natural history of brain involvement.
The nicotinic acetylcholine receptor (nAChR) agonist nicotine and the noradrenaline transporter inhibitor atomoxetine are widely studied substances due to their propensity to alleviate cognitive deficits in psychiatric and neurological patients and their beneficial effects on some aspects of cognitive functions in healthy individuals. However, despite growing evidence of acetylcholine-noradrenaline interactions, there are only very few direct comparisons of the two substances. Here, we investigated the effects of nicotine and atomoxetine on response inhibition in the stop-signal task and we characterised the neural correlates of these effects using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T. Nicotine (7 mg dermal patch) and atomoxetine (60 mg per os) were applied to N = 26 young, healthy adults in a double-blind, placebo-controlled, cross-over, within-subjects design. BOLD images were collected during a stop-signal task that controlled for infrequency of stop trials. There were no drug effects on behavioural performance or subjective state measures. However, there was a pronounced upregulation of activation in bilateral prefrontal and left parietal cortex following nicotine during successful compared to unsuccessful stop trials. The effect of nicotine on BOLD during failed stop trials was correlated across individuals with a measure of trait impulsivity. Atomoxetine, however, had no discernible effects on BOLD. We conclude that nicotine effects on brain function during inhibitory control are most pronounced in individuals with higher levels of impulsivity. This finding is compatible with previous evidence of nicotine effects on stop-signal task performance in highly impulsive individuals and implicates the nAChR in the neural basis of impulsivity.
Recent studies suggest the involvement of episodic memory in value-based decisions as a source of information about subjective values of choice options. We therefore tested the link between age-related memory decline and inconsistencies in value-based decisions in 30 cognitively healthy older adults. Within the pre-registered experiment, the inconsistencies were measured in two ways: i) the consistency between stated preferences and revealed choices; ii) the amount of intransitivities in choice triplets, revealed in a forced paired choice task including all possible pairings of 20 food products. Although no significant association of memory functions to number of intransitive triplets was observed, participants with lower memory scores were more likely to choose the item for which they stated a lower preference. The results suggest a higher noise in the underlying preference signal in participants with lower memory. We discuss the results in the context of the unique needs of elderly consumers.
Objective: Childhood maltreatment is a major risk factor for psychopathology associated with interpersonal problems in adulthood, but the etiological pathways involved are still unclear. The authors propose that childhood maltreatment confers risk for dysfunctional behavior in social interactions by altering interpersonal distance preference and the pro- cessing of social touch. Methods: Ninety-two medication-free adults (64 of them female) with low, medium, and high levels of childhood maltreatment were tested with an interpersonal distance par- adigm and subsequently underwent a social touch functional MRI task during which they rated the perceived comfort of slow touch (C-tactile [CT] optimal speed; 5 cm/s) and fast touch (non-CT-optimal speed; 20 cm/s). Results: Participants with high childhood maltreatment levels preferred a larger interpersonal distance and experienced fast touch as less comforting comparedwith participants with no or moderate childhood maltreatment experiences. On the neural level, participants with severe childhood maltreatment ex- hibited exaggerated responses to fast touch in the right so- matosensory and posterior insular cortex, which correlated with lower comfort ratings. Severe childhood maltreatment was associated with decreased activation in the right hippo- campus in response to slow touch. This response pattern was not moderated or mediated by childhood maltreatment– associated region-specific reductions in gray matter volume. Conclusions: The study findings suggest that higher child- hood maltreatment levels are associated with hypersensi- tivity characterized by a preference for larger interpersonal distance and discomfort of fast touch. These dysregulations were manifested in a sensory cortical hyperreactivity and limbic CT-related hypoactivation. These results may shed light on why individuals with severe childhood maltreatment exhibit an increased susceptibility to interpersonal dysfunc- tions and psychiatric disorders in adulthood.
A prominent theory of developmental stuttering highlights (dys-)function of the basal ganglia (and in particular the ventral striatum) as a main neural mechanism behind this speech disorder. Although the theory is intriguing, studies on gray matter volume differences in the basal ganglia between people who stutter and control persons have reported heterogeneous findings, either showing more or less gray matter volume of the aforementioned brain structure across the brain's hemispheres. Moreover, some studies did not observe any differences at all. From today's perspective several of the earlier studies are rather underpowered and also used less powerful statistical approaches to investigate differences in brain structure between people who stutter and controls. Therefore, the present study contrasted a comparably larger sample of n = 36 people who stutter with n = 34 control persons and applied the state of the art DARTEL algorithm (Diffeomorphic Anatomical Registration Through Exponentiated Lie algebra) to analyze the available brain data. In the present data set stuttering was associated with higher gray matter volume of the right caudate and putamen region of the basal ganglia in patients. Our observation strongly supports a recent finding reporting a larger nucleus accumbens in the right hemisphere in people who stutter when compared to control persons. The present findings are discussed in the context of both compensatory effects of the brain and putative therapeutic effects due to treatment of stuttering.
Aim: Meta-analyses indicate positive effects of both antipsychotic and cognitive-behavioural interventions in subjects clinically at high risk (CHR) for psychosis in terms of a delay or prevention of psychotic disorders. However, these effects have been limited regarding social functioning and the relative efficacy of both types of interventions remains unclear. Furthermore, neuroprotective substances seem to be a promising alternative agent in psychosis-prevention as they are associated with few and weak side-effects. Methods: In this multi-centre randomized controlled trial (RCT), we investigate the effects of two interventions on transition to psychosis and social functioning: (a) an integrated preventive psychological intervention (IPPI) including stress-/symptom-management and social-cognitive remediation; (b) N-acetyl-l-cysteine (NAC) as a pharmacological intervention with glutamatergic, neuroprotective and anti-inflammatory capabilities. Results: This is a double-blind, placebo-controlled RCT with regard to NAC and a single-blind RCT with regard to IPPI using a 2 × 2-factorial design to investigate the individual and combined preventive effects of both interventions. To this aim, a total of 200 CHR subjects will be randomized stratified by site to one of four conditions: (a) IPPI and NAC; (b) IPPI and Placebo; (c) NAC and psychological stress management; (d) Placebo and psychological stress management. Interventions are delivered over 26 weeks with a follow-up period of 12 months. Conclusion: This paper reports on the rationale and protocol of an indicated prevention trial to detect the most effective and tolerable interventions with regard to transition to psychosis as well as improvements in social functioning, and to evaluate the synergistic effects of these interventions.
Distinguishing animate from inanimate objects is fundamental for social perception in humans and animals. Visual motion cues indicative of self-propelled object motion are useful for animacy perception: they can be detected over a wide expanse of visual field, at distance and in low visibility conditions, can attract attention and provide clues about object behaviour. However, the neural correlates of animacy perception evoked exclusively by visual motion cues, i.e. not relying on form, background or visual context, are unclear. We aimed to address this question in four psychophysical experiments in humans, two of which performed during neuroimaging. The stimulus was a single dot with constant form that moved on a blank background and evoked controlled degrees of perceived animacy through parametric variations of self-propelled motion cues. BOLD signals reflecting perceived animacy in a graded manner irrespective of eye movements were found in one intraparietal region. Additional whole-brain and region-of-interest analyses revealed no comparable effects in brain regions associated with social processing or other areas. Our study shows that animacy perception evoked solely by visual motion cues, a basic perceptual process in social cognition, engages brain regions not primarily associated with social cognition.
Social interactions have a major impact on well-being. While many individuals actively seek social situations, others avoid them, at great cost to their private and professional life. The neural mechanisms underlying individual differences in social approach or avoidance tendencies are poorly understood. Here we estimated people's subjective value of engaging in a social situation. In each trial, more or less socially anxious participants chose between an interaction with a human partner providing social feedback and a monetary amount. With increasing social anxiety, the subjective value of social engagement decreased; amygdala BOLD response during decision-making and when experiencing social feedback increased; ventral striatum BOLD response to positive social feedback decreased; and connectivity between these regions during decision-making increased. Amygdala response was negatively related to the subjective value of social engagement. These findings suggest a relation between trait social anxiety / social avoidance and activity in a subcortical network during social decision-making.
Abstract People tend to lie in varying degrees. To advance our understanding of the underlying neural mechanisms of this heterogeneity, we investigated individual differences in self‐serving lying. We performed a functional magnetic resonance imaging study in 37 participants and introduced a color‐reporting game where lying about the color would in general lead to higher monetary payoffs but would also be punished if get caught. At the behavioral level, individuals lied to different extents. Besides, individuals who are more dishonest showed shorter lying response time, whereas no significant correlation was found between truth‐telling response time and the degree of dishonesty. At the neural level, the left caudate, ventromedial prefrontal cortex (vmPFC), right inferior frontal gyrus (IFG), and left dorsolateral prefrontal cortex (dlPFC) were key regions reflecting individual differences in making dishonest decisions. The dishonesty associated activity in these regions decreased with increased dishonesty. Subsequent generalized psychophysiological interaction analyses showed that individual differences in self‐serving lying were associated with the functional connectivity among the caudate, vmPFC, IFG, and dlPFC. More importantly, regardless of the decision types, the neural patterns of the left caudate and vmPFC during the decision‐making phase could be used to predict individual degrees of dishonesty. The present study demonstrated that lying decisions differ substantially from person to person in the functional connectivity and neural activation patterns which can be used to predict individual degrees of dishonesty.
Internet gaming disorder represents a growing health issue. Core symptoms include unsuccessful attempts to control the addictive patterns of behavior and continued use despite negative consequences indicating a loss of regulatory control. Previous studies revealed brain structural deficits in prefrontal regions subserving regulatory control in individuals with excessive Internet use. However, because of the cross-sectional nature of these studies, it remains unknown whether the observed brain structural deficits preceded the onset of excessive Internet use. Against this background, the present study combined a cross-sectional and longitudinal design to determine the consequences of excessive online video gaming. Forty-one subjects with a history of excessive Internet gaming and 78 gaming-naive subjects were enrolled in the present study. To determine effects of Internet gaming on brain structure, gaming-naive subjects were randomly assigned to 6 weeks of daily Internet gaming (training group) or a non-gaming condition (training control group). At study inclusion, excessive Internet gamers demonstrated lower right orbitofrontal gray matter volume compared with Internet gaming-naive subjects. Within the Internet gamers, a lower gray matter volume in this region was associated with higher online video gaming addiction severity. Longitudinal analysis revealed initial evidence that left orbitofrontal gray matter volume decreased during the training period in the training group as well as in the group of excessive gamers. Together, the present findings suggest an important role of the orbitofrontal cortex in the development of Internet addiction with a direct association between excessive engagement in online gaming and structural deficits in this brain region.
Animal models of addiction suggest that the transition from incentive-driven to habitual and ultimately compulsive drug use is mediated by a shift from ventral to dorsal striatal cue-control over drug seeking. Previous studies in human cannabis users reported elevated trait impulsivity and cue-reactivity in striatal circuits, however, these studies were not able to separate addiction-related from exposure-related adaptations. To differentiate the adaptive changes, the present functional magnetic resonance imaging study examined behavioral and neural cue-reactivity in dependent (n = 18) and non-dependent (n = 20) heavy cannabis users and a non-using reference group (n = 44). Irrespective of dependence status, cannabis users demonstrated elevated trait impulsivity as well as increased ventral striatal reactivity and striato-frontal coupling in response to drug cues. Dependent users selectively exhibited dorsal-striatal reactivity and decreased striato-limbic coupling during cue-exposure. An exploratory analysis revealed that higher ventral caudate cue-reactivity was associated with stronger cue-induced arousal and craving in dependent users, whereas this pattern was reversed in non-dependent users. Together the present findings suggest that an incentive sensitization of the ventral striatal reward system may promote excessive drug use in humans, whereas adaptations in dorsal striatal systems engaged in habit formation may promote the transition to addictive use.
Public perception of cannabis as relatively harmless, alongside claimed medical benefits, have led to moves towards its legalization. Yet, long-term consequences of cannabis dependence, and whether they differ qualitatively from other drugs, are still poorly understood. A key feature of addictive drugs is that chronic use leads to adaptations in striatal reward processing, blunting responsivity to the substance itself and natural (non-drug) rewards. Against this background, the present study investigated whether cannabis dependence is associated with lasting alterations in behavioral and neural responses to social reward in 23 abstinent cannabis-dependent men and 24 matched non-using controls. In an interpersonal pleasant touch fMRI paradigm, participants were led to believe they were in physical closeness of or touched (CLOSE, TOUCH) by either a male or female experimenter (MALE, FEMALE), allowing contextual modulation of the perceived pleasantness and associated neural responses. Upon female compared to male touch, dependent cannabis users displayed a significantly attenuated increase of pleasantness experience compared to healthy controls. Controls responded to female as compared to male interaction with increased striatal activation whereas cannabis users displayed the opposite activation pattern, with stronger alterations being associated with a higher lifetime exposure to cannabis. Neural processing of pleasant touch in dependent cannabis users was found to be intact. These findings demonstrate that cannabis dependence is linked to blunted striatal processing of non-drug rewards and suggest that these alterations may contribute to social processing deficits.
2018
Cooperation problems are at the heart of many societal and environmental problems. Prominent solutions frequently rely on monitoring and punishment by central authorities. In recent years, the focus has shifted to decentralized approaches with mutual monitoring and social sanctions to foster cooperation. In this paper, we empirically test for the role of a specific form of social punishment, namely sanctions that are unobservable at first and only applied with a delay. We observe that in particular the combination of such unobservable sanctions with immediately observable sanctions strongly enhances cooperation within groups. Strikingly, this improvement is not caused by an extensive use of both forms of punishment. Our data suggest that the mere thread of unobservable sanctions increases the effectiveness of observable punishment.
We elicit individual-level peer-punishment types in a cooperation (social dilemma) and a coordination (weakest link) problem. In line with previous literature, we find heterogeneity in peer-punishment in both environments. Comparing punishment behavior across the two environments within subject, we observe a high degree of individuals’ punishment type stability. However, the aggregate punishment demand is higher in the weakest-link game. The difference between the two environments is driven by subjects whose behavioral types are inconsistent rather than by a change in the punishment demand of those who punish in both environments.
We explore the relationship between individuals’ disposition to cooperate and their inclination to engage in peer punishment as well as their relative importance for mitigating social dilemmas. Using a novel strategy-method approach we identify individual punishment patterns and link them with individual cooperation patterns. Classifying N = 628 subjects along these two dimensions documents that cooperation and punishment patterns are intuitively aligned for most individuals. However, the data also reveal a sizable share of free-riders that punish pro-socially and conditional cooperators that do not engage in punishment. Analyzing the interplay between types in an additional experiment, we show that pro-social punishers are more crucial for achieving cooperation than conditional cooperators. Incorporating information on punishment types explains large amounts of the between and within group variation in cooperation.
Recent developments in the field of artificial intelligence and data analytics are facilitating the automation of some consumer chores (e.g., in smart homes and in self-driving cars) and allow the emergence of big-data-driven, micro-targeting marketing practices (e.g., personalized content recommendation algorithms). We contend that those developments can generate a tension for marketers, consumers, and policy makers: They can, on the one hand, contribute to consumer well-being by making consumer choices easier, more practical, and more efficient. On the other hand, they can also undermine consumers' sense of autonomy, the absence of which can be detrimental to consumer well-being. Drawing on diverse perspectives from marketing, economics, philosophy, neuroscience, and psychology, we explore how consumers' sense of autonomy in making choices affects their well-being. We discuss how new technologies may enhance or diminish consumers' perceptions of being in control of their choices and how either of those can, in turn, enhance of detract from consumer well-being. Building on this, we identify open research questions in the domain of choice, well-being, and consumer welfare, and suggest avenues for future research.
Faces that move contain rich information about facial form, such as facial features and their configuration, alongside the motion of those features. During social interactions, humans constantly decode and integrate these cues. To fully understand human face perception, it is important to investigate what information dynamic faces convey and how the human visual system extracts and processes information from this visual input. However, partly due to the difficulty of designing well-controlled dynamic face stimuli, many face perception studies still rely on static faces as stimuli. Here, we focus on evidence demonstrating the usefulness of dynamic faces as stimuli, and evaluate different types of dynamic face stimuli to study face perception. Studies based on dynamic face stimuli revealed a high sensitivity of the human visual system to natural facial motion and consistently reported dynamic advantages when static face information is insufficient for the task. These findings support the hypothesis that the human perceptual system integrates sensory cues for robust perception. In the present paper, we review the different types of dynamic face stimuli used in these studies, and assess their usefulness for several research questions. Natural videos of faces are ecological stimuli but provide limited control of facial form and motion. Point-light faces allow for good control of facial motion but are highly unnatural. Image-based morphing is a way to achieve control over facial motion while preserving the natural facial form. Synthetic facial animations allow separation of facial form and motion to study aspects such as identity-from-motion. While synthetic faces are less natural than videos of faces, recent advances in photo-realistic rendering may close this gap and provide naturalistic stimuli with full control over facial motion. We believe that many open questions, such as what dynamic advantages exist beyond emotion and identity recognition and which dynamic aspects drive these advantages, can be addressed adequately with different types of stimuli and will improve our understanding of face perception in more ecological settings.
What cortical mechanisms allow humans to easily discern the expression or identity of a face? Subjects detected changes in expression or identity of a stream of dynamic faces while we measured BOLD responses from topo-graphically and functionally defined areas throughout the visual hierarchy. Responses in dorsal areas increased during the expression task, whereas responses in ventral areas increased during the identity task, consistent with previous studies. Similar to ventral areas, early visual areas showed increased activity during the identity task. If visual responses are weighted by perceptual mechanisms according to their magnitude, these increased responses would lead to improved attentional selection of the task-appropriate facial aspect. Alternatively, increased responses could be a signature of a sensitivity enhancement mechanism that improves representations of the attended facial aspect. Consistent with the latter sensitivity enhancement mechanism, attending to expression led to enhanced decoding of exemplars of expression both in early visual and dorsal areas relative to attending identity. Similarly, decoding identity exemplars when attending to identity was improved in dorsal and ventral areas. We conclude that attending to expression or identity of dynamic faces is associated with increased selectivity in representations consistent with sensitivity enhancement.
We have built a hyperspectral database of 42 fruits and vegetables. Both the outside (skin) and inside of the objects were imaged. We used a Specim VNIR HS-CL-30-V8E-OEM mirror-scanning hyperspectral camera and took pictures at a spatial resolution of ∼57 px/deg∼57 px/deg by 800 pixels at a wavelength resolution of ∼1.12 nm∼1.12 nm. A stable, broadband illuminant was used. Images and software are freely available on our webserver (http://www.allpsych.uni-giessen.de/GHIFVD; pronounced “gift”). We performed two kinds of analyses on these images. First, when comparing the insides and outsides of the objects, we observed that the insides were lighter than the skins, and that the hues of the insides and skins were significantly correlated (circular correlation=0.638correlation=0.638). Second, we compared the color distribution within each object to corresponding human color discrimination thresholds. We found a significant correlation (0.75) between the orientation of ellipses fit to the chromaticity distributions of our fruits and vegetables with the orientations of interpolated MacAdam discrimination ellipses. This indicates a close relationship between sensory processing and the characteristics of environmental objects.
People tend to pay the generosity they receive from a person forward to someone else even if they have no chance to reciprocate directly. This phenomenon, known as paying-it-forward (PIF) reciprocity, crucially contributes to the maintenance of a cooperative human society by passing kindness among strangers and has been widely studied in evolutionary biology. To further examine its neural implementation and underlying computations, we used functional magnetic resonance imaging (fMRI) together with computational modeling. In a modified PIF paradigm, participants first received a monetary split (i.e., greedy, equal, or generous) from either a human partner or a computer. They then chose between two options involving additional amounts of money to be allocated between themselves and an uninvolved person. Behaviorally, people forward the previously-received greed/generosity towards a third person. The social impact of previous treatments is integrated into computational signals in the ventromedial prefrontal cortex (vmPFC) and the right temporoparietal junction (TPJ) during subsequent decision making. Our findings provide insights to understand the proximal origin of PIF reciprocity.
People differ greatly in their financial risk taking behaviour. This heterogeneity has been associated with differences in brain activity, but only in laboratory settings using constrained behaviours. However, it is important to understand how these measures transfer to real life conditions, because the willingness to invest in riskier assets has a direct and considerable effect on long-term wealth accumulation. In a large fMRI study of 157 working age men (39.0 ± 6.4 SD years), we first show that activity in the anterior insula during the assessment of risky vs. safe choices in an investing task is associated with self-reported real-life active stock trading. We then show that this association remains intact when we control for financial constraints, education, the understanding of financial matters, and cognitive abilities. Finally, we use comprehensive measures of preferences and beliefs about risk taking to show that these two channels mediate the association between brain activation in the anterior insula and real-life active stock trading.
Objective: To investigate the clinical and surgical outcome correlates of preoperative hippocampal subfield volumes in patients with refractory temporal lobe epilepsy (TLE) using a new magnetic resonance imaging (MRI) multisequence segmentation technique. Methods: We recruited 106 patients with TLE and hippocampal sclerosis (HS) who underwent conventional T1-weighted and T2 short TI inversion recovery MRI. An automated hippocampal segmentation algorithm was used to identify twelve subfields in each hippocampus. A total of 76 patients underwent amygdalohippocampectomy and postoperative seizure outcome assessment using the standardized ILAE classification. Semiquantitative hippocampal internal architecture (HIA) ratings were correlated with hippocampal subfield volumes. Results: Patients with left TLE had smaller volumes of the contralateral presubiculum and hippocampus-amygdala transition area compared to those with right TLE. Patients with right TLE had reduced contralateral hippocampal tail volumes and improved outcomes. In all patients, there were no significant relationships between hippocampal subfield volumes and clinical variables such as duration and age at onset of epilepsy. There were no significant differences in any hippocampal subfield volumes between patients who were rendered seizure free and those with persistent postoperative seizure symptoms. Ipsilateral but not contralateral HIA ratings were significantly correlated with gross hippocampal and subfield volumes. Conclusions: Our results suggest that ipsilateral hippocampal subfield volumes are not related to the chronicity/severity of TLE. We did not find any hippocampal subfield volume or HIA rating differences in patients with optimal and unfavorable outcomes. In patients with TLE and HS, sophisticated analysis of hippocampal architecture on MRI may have limited value for prediction of postoperative outcome.
The functional connectome represents a comprehensive network map of functional connectivity throughout the human brain. To date, the relationship between the organization of functional connectivity and cognitive performance measures is still poorly understood. In the present study we use resting-state functional magnetic resonance imaging (fMRI) data to explore the link between the functional connectome and working memory capacity in an individual differences design. Working memory capacity, which refers to the maximum amount of context information that an individual can retain in the absence of external stimulation, was assessed outside the MRI scanner and estimated based on behavioral data from a change detection task. Resting-state time series were analyzed by means of voxelwise degree and eigenvector centrality mapping, which are data-driven network analytic approaches for the characterization of functional connectivity. We found working memory capacity to be inversely correlated with both centrality in the right intraparietal sulcus. Exploratory analyses revealed that this relationship was putatively driven by an increase in negative connectivity strength of the structure. This resting-state connectivity finding fits previous task based activation studies that have shown that this area responds to manipulations of working memory load.
Purpose: The aim of this project was to implement an ultra-high field (UHF) optimized double inversion recovery (DIR) sequence for gray matter (GM) imaging, enabling whole brain coverage in short acquisition times (≈ 5 min, image resolution 1 mm 3 ). Methods: A 3D variable flip angle DIR turbo spin echo (TSE) sequence was optimized for UHF application. We implemented an improved, fast, and specific absorption rate (SAR) efficient TSE imaging module, utilizing improved reordering. The DIR preparation was tailored to UHF application. Additionally, fat artifacts were minimized by employing water excitation instead of fat saturation. Results: GM images, covering the whole brain, were acquired in 7 min scan time at 1 mm isotropic resolution. SAR issues were overcome by using a dedicated flip angle calculation considering SAR and SNR efficiency. Furthermore, UHF related artifacts were minimized. Conclusion: The suggested sequence is suitable to generate GM images with whole-brain coverage at UHF. Due to the short total acquisition times and overall robustness, this approac h can potentially enable DIR application in a routine setting and enhance lesion detection in neurological diseases. Magn Reson Med 79:2620–2628, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
A prevailing topic in personality neuroscience is the question how personality traits are reflected in the brain. Functional and structural networks have been examined by functional and structural magnetic resonance imaging, however, the structural correlates of functionally defined networks have not been investigated in a personality context. By using the Temperament and Character Inventory (TCI) and Diffusion Tensor Imaging (DTI), the present study assesses in a sample of 116 healthy participants how personality traits proposed in the framework of the biopsychosocial theory of personality relate to white matter pathways delineated by functional network imaging. We show that the character trait self-directedness relates to the overall microstructural integrity of white matter tracts constituting the salience network as indicated by DTI-derived measures. Self-directedness has been proposed as the executive control component of personality and describes the tendency to stay focused on the attainment of long-term goals. The present finding corroborates the view of the salience network as an executive control network that serves maintenance of rules and task-sets to guide ongoing behavior.
Epilepsy has been associated with a dysfunction of the blood–brain barrier. While there is ample evidence that a dysfunction of the blood–brain barrier contributes to epileptogenesis, blood–brain barrier dysfunction as a consequence of single epileptic seizures has not been systematically investigated. We hypothesized that blood–brain barrier dysfunction is temporally and anatomically associated with epileptic seizures in patients and used a newly-established quantitative MRI protocol to test our hypothesis. Twenty-three patients with epilepsy undergoing inpatient monitoring as part of their presurgical evaluation were included in this study (10 females, mean age ± standard deviation: 28.78 ± 8.45). For each patient, we acquired quantitative T1 relaxation time maps (qT1) after both ictal and interictal injection of gadolinium-based contrast agent. The postictal enhancement of contrast agent was quantified by subtracting postictal qT1 from interictal qT1 and the resulting ΔqT1 was used as a surrogate imaging marker of peri-ictal blood–brain barrier dysfunction. Additionally, the serum concentrations of MMP9 and S100, both considered biomarkers of blood–brain barrier dysfunction, were assessed in serum samples obtained prior to and after the index seizure. Fifteen patients exhibited secondarily generalized tonic-clonic seizures and eight patients exhibited focal seizures at ictal injection of contrast agent. By comparing ΔqT1 of the generalized tonic-clonic seizures and focal seizures groups, the anatomical association between ictal epileptic activity and postictal enhancement of contrast agent could be probed. The generalized tonic-clonic seizures group showed significantly higher ΔqT1 in the whole brain as compared to the focal seizures group. Specific analysis of scans acquired later than 3 h after the onset of the seizure revealed higher ΔqT1 in the generalized tonic-clonic seizures group as compared to the focal seizures group, which was strictly lateralized to the hemisphere of seizure onset. Both MMP9 and S100 showed a significantly increased postictal concentration. The current study provides evidence for the occurrence of a blood–brain barrier dysfunction, which is temporally and anatomically associated with epileptic seizures. qT1 after ictal contrast agent injection is rendered as valuable imaging marker of seizure-associated blood–brain barrier dysfunction and may be measured hours after the seizure. The observation of the strong anatomical association of peri-ictal blood–brain barrier dysfunction may spark the development of new functional imaging modalities for the post hoc visualization of brain areas affected by the seizure.
We investigated how well seven saturation measures defined in CIECAM02, HSV, DKL, LAB, LUV, and CIE 1931 xyY color spaces correspond to human perception of saturation. We used a paradigm that allowed us to measure the perceived saturation of several standard color stimuli in many different directions of color space. We implemented this paradigm at different levels of luminance and varied background luminance relative to the luminance of our color stimuli in order to ensure the generality of our approach. We found that varying background luminance changed the relative saturation of the standard colors. Raising the overall luminance level did not have such an effect. We compared the results of our measurements to the predictions of the seven saturation measures. All of the measures could predict our observers’ judgments of saturation reasonably well. The measures that are based on measurements of discrimination thresholds (LUV, LAB, CIECAM02) performed best on average. However, some of the perceptual effects induced by changing background luminance could not be predicted by any measure.
Current perspectives propose that observer models accounting for both optimal and suboptimal behaviour may yield real progress in understanding perception. We propose that such models could, in addition, be very useful for precisely characterising the variation in perception across healthy participants and those affected by psychiatric disorders, as well as the effects of neuromodulators such as oxytocin.
Mounting evidence emphasizes the usefulness of imaging biomarkers for predicting therapy outcome in major depressive disorder (MDD), in particular building on functional imaging studies of task-based responses to emotional face stimuli and resting state-related connectivity patterns. To explore the possibility that prediction accuracy even in small patient samples would significantly gain from integrating data from different imaging modalities, we acquired functional neuroimaging data both at-rest and during exposure to emotional faces from 21 MDD patients before and 7 weeks after treatment-as-usual, as well as from 20 age- and gender-matched control participants assessed at similar intervals. As expected, MDD patients showed disturbed pre-treatment responses to emotional faces, including left amygdala hyperactivation. Therapeutic outcome correlated with pre-treatment activation, with subgenual cingulate response to emotional faces yielding best results (r values ranging from 0.4 to 0.66). A support vector machine classifier trained on task-based or resting-state data predicted responder status, with the right dorsolateral prefrontal cortex connectivity pattern yielding best accuracy (88.9%). Crucially, combining task-based with resting-state data increased prediction accuracy by 6.5–7.7 percentage points on average. From this pilot study, we conclude that multimodal functional imaging has the potential of improving therapy outcome prediction even in small MDD sample sizes, resulting in about one additional correct classification every 15 patients. The present results inform future studies which are needed to consolidate imaging approaches as a means of establishing precision medicine in psychiatry.
Objective: Recent MRI studies have shown that the orientation of nerve fibres relative to the main magnetic field affects the R2*(= 1/T2*) relaxation rate in white matter (WM) structures. The underlying physical causes have been discussed in several studies but are still not completely understood. However, understanding these effects in detail is of great importance since this might serve as a basis for the development of new diagnostic tools and/or improve quantitative susceptibility mapping techniques. Therefore, in addition to the known angular dependence of R2*, the current study investigates the relationship between fibre orientation and the longitudinal relaxation rate, R1 (= 1/T1), as well as the apparent water content. Materials and methods: For a group of 16 healthy subjects, a series of gradient echo, echo-planar and diffusion weighted images were acquired at 3T from which the decay rates, the apparent water content and the diffusion direction were reconstructed. The diffusion weighted data were used to determine the angle between the principle fibre direction and the main magnetic field to examine the angular dependence of R1 and apparent water content. Results: The obtained results demonstrate that both parameters depend on the fibre orientation and exhibit a positive correlation with the angle between fibre direction and main magnetic field. Conclusion: These observations could be helpful to improve and/or constrain existing biophysical models of brain microstructure by imposing additional constraints resulting from the observed angular dependence R1 and apparent water content in white matter.
Although research on goal-directed, proactive inhibitory control (IC) and stimulus-driven, reactive IC is growing, no previous study has compared proactive IC in conditions ofuncertainty with regard to upcoming inhibition to conditions ofcertain upcoming IC. Therefore, we investigated effects ofcertainty and uncertainty on behavior and blood oxygen level dependent (BOLD) signal in proactive and reactive IC. In two studies, healthy adults performed saccadic go/no-go and prosaccade/antisaccade tasks. The certainty manipulation had a highly significant behavioral effect in both studies, with inhibitory control being more successful under certain than uncertain conditions on both tasks (p ≤ 0.001). Saccadic go responses were significantly less efficient under conditions of uncertainty than certain responding (p < 0.001). Event-related functional magnetic resonance imaging (fMRI) (one study) revealed a dissociation ofcertainty- and uncertainty-related proactive inhibitory neural correlates in the go/no-go task, with lateral and medial prefrontal and occipital cortex showing stronger deactivations during uncertainty than during certain upcoming inhibition, and lateral parietal cortex being activated more strongly during certain upcoming inhibition than uncertainty or certain upcoming responding. In the antisaccade task, proactive BOLD effects arose due to stronger deactivations in uncertain response conditions ofboth tasks and before certain prosaccades than antisaccades. Reactive inhibition-related BOLD increases occurred in inferior parietal cortex and supramarginal gyrus (SMG) in the go/no-go task only. Proactive ICmay imply focusing attention on the external environment for encoding salient or alerting events as well as inhibitory mechanisms that reduce potentially distracting neural processes. SMG and inferior parietal cortex may play an important role in both proactive and reactive IC of saccades.
Symptomfreiheit sowie Erhalt der Selbstbestimmung über die eigene Lebensführung gehören zu den Zielen der Schizophreniebehandlung. Die erreichten Genesungsraten sind jedoch eher moderat, was sich auch in den langfristigen Kosten für das Gesundheitssystem widerspiegelt. Die Prävention der Schizophrenie, mit dem Ziel attenuierte psychotische Symptome zu diagnostizieren, bevor eine manifeste Schizophrenie auftritt, steht daher im Fokus von Forschung und Praxis. Dazu gehören auch früh einsetzbare moderne Behandlungsmethoden mit geringem Nebenwirkungsprofil wie N-Acetylcystein.
Progressive functional decline in the epilepsies is largely unexplained. We formed the ENIGMA-Epilepsy consortium to understand factors that influence brain measures in epilepsy, pooling data from 24 research centres in 14 countries across Europe, North and South America, Asia, and Australia. Structural brain measures were extracted from MRI brain scans across 2149 individuals with epilepsy, divided into four epilepsy subgroups including idiopathic generalized epilepsies (n =367), mesial temporal lobe epilepsies with hippocampal sclerosis (MTLE; left, n = 415; right, n = 339), and all other epilepsies in aggregate (n = 1026), and compared to 1727 matched healthy controls. We ranked brain structures in order of greatest differences between patients and controls, by meta-Analysing effect sizes across 16 subcortical and 68 cortical brain regions. We also tested effects of duration of disease, age at onset, and age-by-diagnosis interactions on structural measures. We observed widespread patterns of altered subcortical volume and reduced cortical grey matter thickness. Compared to controls, all epilepsy groups showed lower volume in the right thalamus (Cohen's d = â '0.24 to â '0.73; P < 1.49 × 10 â '4), and lower thickness in the precentral gyri bilaterally (d = â '0.34 to â '0.52; P < 4.31 × 10 â '6). Both MTLE subgroups showed profound volume reduction in the ipsilateral hippocampus (d = â '1.73 to â '1.91, P < 1.4 × 10 â '19), and lower thickness in extrahippocampal cortical regions, including the precentral and paracentral gyri, compared to controls (d = â '0.36 to â '0.52; P < 1.49 × 10 â '4). Thickness differences of the ipsilateral temporopolar, parahippocampal, entorhinal, and fusiform gyri, contralateral pars triangularis, and bilateral precuneus, superior frontal and caudal middle frontal gyri were observed in left, but not right, MTLE (d = â '0.29 to â '0.54; P < 1.49 × 10 â '4). Contrastingly, thickness differences of the ipsilateral pars opercularis, and contralateral transverse temporal gyrus, were observed in right, but not left, MTLE (d = â '0.27 to â '0.51; P < 1.49 × 10 â '4). Lower subcortical volume and cortical thickness associated with a longer duration of epilepsy in the all-epilepsies, all-other-epilepsies, and right MTLE groups (beta, b < â '0.0018; P < 1.49 × 10 â '4). In the largest neuroimaging study of epilepsy to date, we provide information on the common epilepsies that could not be realistically acquired in any other way. Our study provides a robust ranking of brain measures that can be further targeted for study in genetic and neuropathological studies. This worldwide initiative identifies patterns of shared grey matter reduction across epilepsy syndromes, and distinctive abnormalities between epilepsy syndromes, which inform our understanding of epilepsy as a network disorder, and indicate that certain epilepsy syndromes involve more widespread structural compromise than previously assumed.
The transition from voluntary to addictive behavior is characterized by a loss of regulatory control in favor of reward driven behavior. Animal models indicate that this process is neurally underpinned by a shift in ventral to dorsal striatal control of behavior, however this shift has not been directly examined in humans. Against this background the present resting state fMRI study employed a two-step approach to (1) precisely map striatal alterations using a novel, data-driven network classification strategy combining Intrinsic Connectivity Contrast (ICC) with Multivoxel Pattern Analysis (MVPA) and, (2) to determine whether a ventral to dorsal striatal shift in connectivity with reward and and regulatory control regions can be observed in abstinent (28 days) male cannabis-dependent individuals (n = 24) relative to matched controls (n = 28). Network classification revealed that the groups can be reliably discriminated by global connectivity profiles of two striatal regions that mapped onto the ventral (nucleus accumbens) and dorsal striatum (caudate). Subsequent functional connectivity analysis demonstrated a relative shift between ventral and dorsal striatal communication with fronto-limbic regions that have been consistently involved in reward processing (rostral ACC) and executive / regulatory functions (dorsomedial PFC). Specifically, in the cannabis dependent subjects connectivity between the ventral striatum with the rostral ACC increased, whereas both striatal regions were uncoupled from the regulatory dorsomedial PFC. Together these findings suggest a shift in the balance between dorsal and ventral striatal control in cannabis dependence. Similar changes have been observed in animal models and may promote the loss of control central to addictive behavior.
Across species, the neuropeptide oxytocin has been associated with affiliative and social approach behavior. It has been suggested to exert its effects by modulating neural circuitry underlying anxiety, affiliative motivation, and social salience. The present study aims to investigate differences in subregional amygdala resting-state connectivity in healthy adult carriers of different genotypes of the oxytocin receptor (OXTR) gene polymorphism rs2268498. Previous studies have associated this polymorphic locus with social cognitive and affiliative phenotypes. The amygdala qualifies as a reasonable target due to its broad implication in emotional and social cognitive processing as well as its key role in mediating the behavioral effects of oxytocin. Whole brain seed-based functional connectivity analyses for the basolateral, centromedial and superficial amygdala revealed stronger resting-state connectivity of all amygdala subregions to the fusiform and inferior occipital gyrus in TT-carriers compared to C-allele carriers. Additional modulations were found for the centromedial amygdala which showed stronger resting-state connectivity to inferior frontal regions and the insula in C-allele carriers and to brainstem regions in TT-carriers. Our findings not only show the importance of oxytocin functioning in amygdalar neuronal signaling but also emphasize the need to investigate the amygdalar subregions individually instead of the amygdala as a whole. In summary, the present study is the first to characterize the impact of genetic variation of the OXTR gene with known functional consequences on widespread changes in a functional brain network originating from the amygdala.
Rationale: Intact cognitive and emotional functioning is vital for the long-term success of addiction treatment strategies. Accumulating evidence suggests an association between chronic marijuana use and lasting alterations in cognitive brain function. Despite initial evidence for altered emotion processing in dependent marijuana users after short abstinence periods, adaptations in the domain of emotion processing after longer abstinence remain to be determined. Objective and methods: Using task-based and resting state fMRI, the present study investigated emotion processing in 19 dependent marijuana users and 18 matched non-using controls after an abstinence period of > 28 days. Results: Relative to the control subjects, negative emotional stimuli elicited increased medial orbitofrontal cortex (mOFC) activity and stronger mOFC-dorsal striatal and mOFC-amygdala functional coupling in dependent marijuana users (p < 0.022, FWE-corrected). Furthermore, mOFC-dorsal striatal functional connectivity was increased at rest in marijuana users (p < 0.03, FWE-corrected). Yet, processing of positive stimuli and subjective ratings of valence and arousal were comparable in both groups. Conclusions: Together, the present findings provide the first evidence for persisting emotion processing alterations in dependent marijuana users. Alterations might reflect long-term neural adaptations as a consequence of chronic marijuana use or predisposing risk factors for the development of marijuana dependence.
2017
Animal studies suggest that N-methyl-D-aspartate receptor (NMDAR) dependent signalling in limbic and prefrontal regions is critically involved in both cognitive and emotional functions. In humans, ketamine-induced transient, and disorder associated chronic NMDAR hypofunction (i.e. in schizophrenia) has been associated with deficient performance in the domains of memory and higher-order emotional functioning, as well as altered neural activity in the underlying limbic-prefrontal circuits. To model the effects of NMDAR hypofunction on the integration of emotion and cognition the present pharmacological fMRI study applied the NMDAR antagonist ketamine (target plasma level=100 ng/ml) to 21 healthy volunteers in a within-subject placebo-controlled crossover design during encoding of neutral, positive and negative pictures. Our results show that irrespective of emotion, ketamine suppressed parahippocampal and medial prefrontal activity. In contrast, ketamine selectively increased amygdala and orbitofrontal activity during successful encoding of negative stimuli. On the network level ketamine generally increased medial prefrontal-parahippocampal coupling while specifically decreasing amygdala-orbitofrontal interplay during encoding of negative stimuli. On the behavioural level, ketamine produced generally decreased memory performance and abolished the emotional enhancement of memory after a wash-out period of 5 days. The present findings suggest that ketamine produces general as well as valence-specific effects during emotional memory formation. The pattern partly overlaps with alterations previously observed in patients with schizophrenia.
Understanding processes performed by an intact visual cortex as the basis for developing methods that enhance or restore visual perception is of great interest to both researchers and medical practitioners. Here, we explore whether contrast sensitivity, a main function of the primary visual cortex (V1), can be improved in healthy subjects by repetitive, noninvasive anodal transcranial direct current stimulation (tDCS). Contrast perception was measured via threshold perimetry directly before and after intervention (tDCS or sham stimulation) on each day over 5 consecutive days (24 subjects, double-blind study). tDCS improved contrast sensitivity from the second day onwards, with significant effects lasting 24 h. After the last stimulation on day 5, the anodal group showed a significantly greater improvement in contrast perception than the sham group (23 vs. 5%). We found significant long-term effects in only the central 2–4° of the visual field 4 weeks after the last stimulation. We suspect a combination of two factors contributes to these lasting effects. First, the V1 area that represents the central retina was located closer to the polarization electrode, resulting in higher current density. Second, the central visual field is represented by a larger cortical area relative to the peripheral visual field (cortical magnification). This is the first study showing that tDCS over V1 enhances contrast perception in healthy subjects for several weeks. This study contributes to the investigation of the causal relationship between the external modulation of neuronal membrane potential and behavior (in our case, visual perception). Because the vast majority of human studies only show temporary effects after single tDCS sessions targeting the visual system, our study underpins the potential for lasting effects of repetitive tDCS-induced modulation of neuronal excitability.
A core prediction of recent “dual-self” models is that risk attitudes depend on self-control. While these models have received a lot of attention, empirical evidence regarding their predictions is lacking. We derive hypotheses from three prominent models for choices between risky monetary payoffs under regular and reduced self-control. We test the hypotheses in a lab experiment, using a well-established ego depletion task to reduce self-control, and measuring risk attitudes via finely graduated choice lists. Manipulation checks document the effectiveness of the depletion task. We find no systematic evidence in favor of the theoretical predictions. In particular, depletion does not increase risk aversion.
Third-party altruistic decision-making has been shown to be modulated by other-regarding attention (e.g., focusing on the offender's crime or the victim's situation especially in judicial judgment). However, the neural mechanisms underlying this modulation remain poorly understood. In this fMRI study, participants voluntarily decided if they wanted to punish the first-party offender or help the second-party victim using their own monetary endowment in an unfair context. Particularly, before deciding they were asked to focus on the (un)fairness of the offender proposing the offer (offender-focused block, OB), the feeling of the victim receiving this offer (victim-focused block, VB), or without any specific focus (baseline block, BB). We found that compared to BB participants punished more frequently and prolonged help choices in OB, whereas they helped more frequently in VB. These findings were accompanied by an increased activation in the temporo-parietal junction (TPJ) during decision making in OB and VB. Moreover, regions relevant to cognitive control (esp. IFG/AI and the dorsal anterior cingulate cortex) were strongly recruited during specific choices conflicting the attention focus (e.g., choosing help in OB). Our findings revealed how other-regarding attention modulates third-party altruistic decision-making at the neural level.
According to Jaak Panksepp's Affective Neuroscience Theory and the derived self-report measure, the Affective Neuroscience Personality Scales (ANPS), differences in the responsiveness of primary emotional systems form the basis of human personality. In order to investigate neuronal correlates of personality, the underlying neuronal circuits of the primary emotional systems were analyzed in the present fMRI-study by associating the ANPS to functional connectivity in the resting brain. N=120 healthy participants were invited for the present study. The results were reinvestigated in an independent, smaller sample of N=52 participants. A seed-based whole brain approach was conducted with seed-regions bilaterally in the basolateral and superficial amygdalae. The selection of seed-regions was based on meta-analytic data on affective processing and the Juelich histological atlas. Multiple regression analyses on the functional connectivity maps revealed associations with the SADNESS-scale in both samples. Functional resting-state connectivity between the left basolateral amygdala and a cluster in the postcentral gyrus, and between the right basolateral amygdala and clusters in the superior parietal lobe and subgyral in the parietal lobe was associated with SADNESS. No other ANPS-scale revealed replicable results. The present findings give first insights into the neuronal basis of the SADNESS-scale of the ANPS and support the idea of underlying neuronal circuits. In combination with previous research on genetic associations of the ANPS functional resting-state connectivity is discussed as a possible endophenotype of personality.
Background
Exercise interventions to prevent dementia and delay cognitive decline have gained considerable attention in recent years. Human and animal studies have demonstrated that regular physical activity targets brain function by increasing cognitive reserve. There is also evidence of structural changes caused by exercise in preventing or delaying the genesis of neurodegeneration. Although initial studies indicate enhanced cognitive performance in patients with mild cognitive impairment (MCI) following an exercise intervention, little is known about the effect of an extensive, controlled and regular exercise regimen on the neuropathology of patients with MCI. This study aims to determine the effects of an extensive exercise programme on the progression of MCI.
Methods/design
This randomised controlled clinical intervention study will take place across three European sites. Seventy-five previously sedentary patients with a clinical diagnosis of MCI will be recruited at each site. Participants will be randomised to one of three groups. One group will receive a standardised 1-year extensive aerobic exercise intervention (3 units of 45 min/week). The second group will complete stretching and toning (non-aerobic) exercise (3 units of 45 min/week) and the third group will act as the control group. Change in all outcomes will be measured at baseline (T0), after six months (T1) and after 12 months (T2). The primary outcome, cognitive performance, will be determined by a neuropsychological test battery (CogState battery, Trail Making Test and Verbal fluency). Secondary outcomes include Montreal Cognitive Assessment (MoCA), cardiovascular fitness, physical activity, structural changes of the brain, quality of life measures and measures of frailty. Furthermore, outcome variables will be related to genetic variations on genes related to neurogenesis and epigenetic changes in these genes caused by the exercise intervention programme.
Discussion
The results will add new insights into the prevailing notion that exercise may slow the rate of cognitive decline in MCI.
Consistent decisions are intuitively desirable and theoretically important for utility maximization. Neuroeconomics has established the neurobiological substrate of value representation, but brain regions that provide input to this network is less explored. The constructed-preference tradition within behavioral decision research gives a critical role to associative cognitive processes, suggesting a hippocampal role in making consistent decisions. We compared the performance of 31 patients with mediotemporal lobe (MTL) epilepsy and hippocampal lesions, 30 patients with extratemporal lobe epilepsy, and 30 healthy controls on two tasks: binary choices between candy bars based on their preferences and a number-comparison control task where the larger number is chosen. MTL patients made more inconsistent choices than the other two groups for the value-based choice but not the number-comparison task. These inconsistencies correlated with the volume of compromised hippocampal tissue. These results add to increasing evidence on a critical involvement of the MTL in preference construction and value-based choices.
A core prediction of recent “dual-self” models is that risk attitudes depend on self-control. While these models have received a lot of attention, empirical evidence regarding their predictions is lacking. We derive hypotheses from three prominent models for choices between risky monetary payoffs under regular and reduced self-control. We test the hypotheses in a lab experiment, using a well-established ego depletion task to reduce self-control, and measuring risk attitudes via finely graduated choice lists. Manipulation checks document the effectiveness of the depletion task. We find no systematic evidence in favor of the theoretical predictions. In particular, depletion does not increase risk aversion.
Delay discounting (DD) refers to the phenomenon that individuals discount future consequences. Previous studies showed that future imagination reduces DD, which was mediated by functional connectivity between medial prefrontal valuation areas and a key region for episodic memory (hippocampus). Future imagination involves an initial period of construction and a later period of elaboration, with the more elaborative latter period recruiting more cortical regions. This study examined whether elaborative future imagination modulated DD, and if so, what are the underlying neural substrates. It was assumed that cortical areas contribute to the modulation effect during the later period of imagination. Since future imagination is supported by episodic memory capacity, we additionally hypothesize that the neural network underlying the modulation effect is related to individual episodic memory capacity. Twenty-two subjects received an extensive interview on personal future events, followed by an fMRI DD experiment with and without the need to performelaborative future imagination simultaneously. Subjects’ episodic memory capacity was also assessed. Behavioral results replicate previous findings of a reduced discount rate in the DD plus imagination condition compared to the DD only condition. The behavioral effect positively correlated with: (i) subjective value signal changes in midline brain structures during the initial imagination period; and (ii) signal changes in left prefrontoparietal areas during the later imagination period. Generalized psychophysiological interaction (gPPI) analyses reveal positive correlations between the behavioral effect and functional connectivity among the following areas: right anterior cingulate cortex (ACC) and left hippocampus; left inferior parietal cortex (IPC) and left hippocampus; and left IPCand bilateral occipital cortices. These changes in functional connectivity are also associated with episodic memory capacity. A hierarchical multiple regression indicates that the model with both the valuation related signal changes in the right ACC and the imagination related signal changes in the left IPC best predicts the reduction in DD. This study illustrates interactions between the left hippocampus and multiple cortical regions underlying the modulation effect of elaborative episodic future imagination, demonstrating, for the first time, empirical support for a relation to individual episodic memory capacity.
Introduction Subjective cognitive decline (SCD) refers to an at-risk state of Alzheimer's disease and subtle cognitive deficits that have been observed in this condition. Currently, it is unknown whether complex cognitive processes relevant to everyday life, such as future-oriented choice behavior, are also altered in SCD. Methods Twenty SCD participants and 24 control (CO) participants took part in a functional magnetic resonance imaging task on intertemporal decisions, with and without simultaneous episodic future imagination. Results SCD participants showed reduced future-oriented choices. Future imagination increased future-oriented choices and was associated with increased brain activation in medial frontal polar cortex, right insular cortex, and anterior cingulate cortex in CO only, not SCD. In addition, more future-oriented choices were associated with hippocampal activation during choice processing in CO only. Discussion Subtle neuronal network disruptions in SCD may underlie their myopic future decisions and lack of modulation of choice behavior by episodic future imagination.
The integration of neuroscientific methods in Information Systems (IS) research to better understand how the brain interacts with IS-relevant context has gained in importance. Many papers that highlight the potential of neuroIS and that discuss methodological issues associated with using functional brain imaging already exist. However, neuroIS researchers have to keep in mind that the emergence of complex mental processes such as trust in IS contexts is based on activity in a network of brain regions rather than on activity in one area alone. Accordingly, we introduce psycho-physiological interaction (PPI) analysis, a technique that one can use to analyze fMRI data. Specifically, we review how one can conduct PPI analysis, provide a concrete research example, and show how this analysis can inform IS trust research. Thus, we introduce neuroIS researchers working in the domain of functional brain imaging to advanced fMRI analyses methods and show, based on the example of trust, how these methods can enhance our understanding of the nature of IS constructs.
The phylogenetically ancient neuropeptide oxytocin has been linked to a plethora of social behaviors. Here, we argue that the action of oxytocin is not restricted to the downstream level of emotional responses, but substantially alters higher representations of attitudes and values by exerting a distant modulatory influence on cortical areas and their reciprocal interplay with subcortical regions and hormonal systems.
Current perspectives on attractiveness-related prosocial biases emphasize the contribution of evolutionarily shaped mating drives. Here, we extend these concepts by highlighting the pivotal role of the hypothalamic peptide oxytocin in augmenting the salience and rewarding value of social stimuli, including the partner's face, thereby fostering social bonding in general and the stability of monogamous pair bonds and offspring care in particular.
Approximately one in every two patients with pharmacoresistant temporal lobe epilepsy will not be rendered completely seizure-free after temporal lobe surgery. The reasons for this are unknown and are likely to be multifactorial. Quantitative volumetric magnetic resonance imaging techniques have provided limited insight into the causes of persistent postoperative seizures in patients with temporal lobe epilepsy. The relationship between postoperative outcome and preoperative pathology of white matter tracts, which constitute crucial components of epileptogenic networks, is unknown. We investigated regional tissue characteristics of preoperative temporal lobe white matter tracts known to be important in the generation and propagation of temporal lobe seizures in temporal lobe epilepsy, using diffusion tensor imaging and automated fibre quantification. We studied 43 patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis and 44 healthy controls. Patients underwent preoperative imaging, amygdalohippocampectomy and postoperative assessment using the International League Against Epilepsy seizure outcome scale. From preoperative imaging, the fimbria-fornix, parahippocampal white matter bundle and uncinate fasciculus were reconstructed, and scalar diffusion metrics were calculated along the length of each tract. Altogether, 51.2% of patients were rendered completely seizure-free and 48.8% continued to experience postoperative seizure symptoms. Relative to controls, both patient groups exhibited strong and significant diffusion abnormalities along the length of the uncinate bilaterally, the ipsilateral parahippocampal white matter bundle, and the ipsilateral fimbria-fornix in regions located within the medial temporal lobe. However, only patients with persistent postoperative seizures showed evidence of significant pathology of tract sections located in the ipsilateral dorsal fornix and in the contralateral parahippocampal white matter bundle. Using receiver operating characteristic curves, diffusion characteristics of these regions could classify individual patients according to outcome with 84% sensitivity and 89% specificity. Pathological changes in the dorsal fornix were beyond the margins of resection, and contralateral parahippocampal changes may suggest a bitemporal disorder in some patients. Furthermore, diffusion characteristics of the ipsilateral uncinate could classify patients from controls with a sensitivity of 98%; importantly, by co-registering the preoperative fibre maps to postoperative surgical lacuna maps, we observed that the extent of uncinate resection was significantly greater in patients who were rendered seizure-free, suggesting that a smaller resection of the uncinate may represent insufficient disconnection of an anterior temporal epileptogenic network. These results may have the potential to be developed into imaging prognostic markers of postoperative outcome and provide new insights for why some patients with temporal lobe epilepsy continue to experience postoperative seizures.AbbreviationsAFQ = automated fibre quantification; DTI = diffusion tensor imaging; ILAE = International League Against Epilepsy; ROC = receiver operating characteristic; TLE = temporal lobe epilepsy.
Purpose A detailed understanding of white matter tract alterations in patients with temporal lobe epilepsy (TLE) is important as it may provide useful information for likely side of seizure onset, cognitive impairment and postoperative prognosis. However, most diffusion-tensor imaging (DTI) studies have relied on manual reconstruction of tract bundles, despite the recent development of automated techniques. In the present study, we used an automated white matter tractography analysis approach to quantify temporal lobe white matter tract alterations in TLE and determine the relationships between tract alterations, the extent of hippocampal atrophy and the chronicity and severity of the disorder. Methods We acquired preoperative T1-weighted and DTI data in 64 patients with well-characterized TLE, with imaging and histopathological evidence of hippocampal sclerosis. Identical acquisitions were collected for 44 age- and sex-matched healthy controls. We employed automatic probabilistic tractography DTI analysis using TRActs Constrained by UnderLying Anatomy (TRACULA) available in context of Freesurfer software for the reconstruction of major temporal lobe tract bundles. We determined the factors influencing probabilistic tract reconstruction and investigated alterations of DTI scalar metrics along white matter tracts with respect to hippocampal volume, which was automatically estimated using Freesurfer's morphometric pipelines. We also explored the relationships between white matter tract alterations and duration of epilepsy, age of onset of epilepsy and seizure burden (defined as a function of seizure frequency and duration of epilepsy). Results Whole-tract diffusion characteristics of patients with TLE differed according to side of epilepsy and were significantly different between patients and controls. Waypoint comparisons along each tract revealed that patients had significantly altered tissue characteristics of the ipsilateral inferior-longitudinal, uncinate fasciculus, superior longitudinal fasciculus and cingulum relative to controls. Changes were more widespread (ipsilaterally and contralaterally) in patients with left TLE while patients with right TLE showed changes that remained spatially confined in ipsilateral tract regions. We found no relationship between DTI alterations and volume of the epileptogenic hippocampus. DTI alterations of anterior ipsilateral uncinate and inferior-longitudinal fasciculus correlated with duration of epilepsy (over and above effects of age) and age at onset of epilepsy. Seizure burden correlated with tissue characteristics of the uncinate fasciculus. Conclusion This study shows that TRACULA permits the detection of alterations of DTI tract scalar metrics in patients with TLE. It also provides the opportunity to explore relationships with structural volume measurements and clinical variables along white matter tracts. Our data suggests that the anterior temporal lobe portions of the uncinate and inferior-longitudinal fasciculus may be particularly vulnerable to pathological alterations in patients with TLE. These alterations are unrelated to the extent of hippocampal atrophy (and therefore potentially mediated by independent mechanisms) but influenced by chronicity and severity of the disorder.
The rich club comprises a densely mutually connected set of hub regions in the brain, thought to serve as a processing and integration core. We assessed the impact of normal variation of the tryptophane hydroxylase 2 gene's promotor region (TPH2 rs4570625) on structural connectivity of the rich club pathways by means of a candidate gene association design. Tryptophane hydroxylase 2 (TPH2) is a rate-limiting enzyme in the biosynthesis of serotonin and is known to inhibit, in addition to its role as a trans-synaptic messenger, axonal and dendritic growth. The TPH2 T-variant has been associated with reduced mRNA expression and reduced serotonin levels, which may particularly influence the development of macroscale anatomical connectivity. Here, we show larger mean connectivity in the rich club in carriers of the T-variant, suggesting potential effects of upregulation of neural connectivity growth in this central core system. In addition, by edge-removal statistics, we show that the TPH2-associated higher levels of rich club connectivity are of importance for the functioning of the total structural network. The observed association is speculated to result from an effect of serotonin levels on brain development, potentially leading to stronger structural connectivity in heavily interconnected hubs.
Dopaminergic neurotransmission in the mesocortical system is crucial for higher order cognition. Common variation on the dopamine D2 receptor (DRD2) gene has been linked to individual differences in dopaminergic signaling and was also repeatedly associated to cognitive markers. The relationship between dopaminergic genetic variants and neurostructural properties of the mesocortical system, however, has received little attention so far. Recently, the direction of a dopaminergic manipulation was predicted from the integrity of fiber tracts between subcortical areas and the frontal lobes. Fiber tract integrity was therefore proposed as an indicator of baseline dopamine activity. This raises the question whether DRD2 variants that relate to dopamine turnaround are also linked to fiber tract integrity. In the present study we assessed associations between the DRD2 rs6277 polymorphism and subcortical connections from connectome maps derived from diffusion weighted imaging in n=105 healthy volunteers (43 males and 62 females). Carriers of the CC genotype who are characterized by elevated striatal dopamine turnaround showed higher integrity in terms of fractional anisotropy on fiber tracts between the basal ganglia and frontal regions compared to carriers of the CT and TT variant. Our results indicate that structural connectivity could serve as a conceptual link between genetically determined individual differences in dopaminergic activity and effects of dopamine challenges on executive functioning.
Never before have individuals had to adapt to social environments defined by such magnitudes of ethnic diversity and cultural differentiation. However, neurobiological evidence informing about strategies to reduce xenophobic sentiment and foster altruistic cooperation with outsiders is scarce. In a series of experiments settled in the context of the current refugee crisis, we tested the propensity of 183 Caucasian participants to make donations to people in need, half of whom were refugees (outgroup) and half of whom were natives (ingroup). Participants scoring low on xenophobic attitudes exhibited an altruistic preference for the outgroup, which further increased after nasal delivery of the neuropeptide oxytocin. In contrast, participants with higher levels of xenophobia generally failed to exhibit enhanced altruism toward the outgroup. This tendency was only countered by pairing oxytocin with peer-derived altruistic norms, resulting in a 74% increase in refugee-directed donations. Collectively, these findings reveal the underlying sociobiological conditions associated with outgroup-directed altruism by showing that charitable social cues co-occurring with enhanced activity of the oxytocin system reduce the effects of xenophobia by facilitating prosocial behavior toward refugees.
A recent study has implicated the nucleus accumbens of the ventral striatum in explaining why online-users spend time on the social network platform Facebook. Here, higher activity of the nucleus accumbens was associated with gaining reputation on social media. In the present study, we touched a related research field. We recorded the actual Facebook usage of N = 62 participants on their smartphones over the course of five weeks and correlated summary measures of Facebook use with gray matter volume of the nucleus accumbens. It appeared, that in particular higher daily frequency of checking Facebook on the smartphone was robustly linked with smaller gray matter volumes of the nucleus accumbens. The present study gives additional support for the rewarding aspects of Facebook usage. Moreover, it shows the feasibility to include real life behavior variables in human neuroscientific research.
IMPORTANCE: During the past 20 years, numerous neuroimaging experiments have investigated aberrant brain activation during cognitive and emotional processing in patients with unipolar depression (UD). The results of those investigations, however, vary considerably; moreover, previous meta-analyses also yielded inconsistent findings. OBJECTIVE: To readdress aberrant brain activation in UD as evidenced by neuroimaging experiments on cognitive and/or emotional processing. DATA SOURCES: Neuroimaging experiments published from January 1,1997, to October 1, 2015, were identified by a literature search of PubMed, Web of Science, and Google Scholar using different combinations of the terms fMRI (functionalmagnetic resonance imaging), PET (positron emission tomography), neural, major depression, depression, major depressive disorder, unipolar depression, dysthymia, emotion, emotional, affective, cognitive, task, memory, working memory, inhibition, control, n-back, and Stroop. STUDY SELECTION: Neuroimaging experiments (using fMRI or PET) reporting whole-brain results of group comparisons between adults with UDand healthy control individuals as coordinates in a standard anatomic reference space and using an emotional or/and cognitive challenging task were selected. DATA EXTRACTION AND SYNTHESIS: Coordinates reported to show significant activation differences between UDand healthy controls during emotional or cognitive processing were extracted. By using the revised activation likelihood estimation algorithm, different meta-analyses were calculated. MAIN OUTCOMES AND MEASURES: Meta-analyses tested for brain regions consistently found to show aberrant brain activation in UD compared with controls. Analyses were calculated across all emotional processing experiments, all cognitive processing experiments, positive emotion processing, negative emotion processing, experiments using emotional face stimuli, experiments with a sex discrimination task, and memory processing. All meta-analyses were calculated across experiments independent of reporting an increase or decrease of activity in major depressive disorder. For meta-analyses with a minimum of 17 experiments available, separate analyses were performed for increases and decreases. RESULTS: In total, 57 studies with 99 individual neuroimaging experiments comprising in total 1058 patients were included; 34 of them tested cognitive and 65 emotional processing. Overall analyses across cognitive processing experiments (P >.29) and across emotional processing experiments (P >.47) revealed no significant results. Similarly, no convergence was found in analyses investigating positive (all P >.15), negative (all P >.76), or memory (all P >.48) processes. Analyses that restricted inclusion of confounds (eg, medication, comorbidity, age) did not change the results. CONCLUSIONS AND RELEVANCE: Inconsistencies exist across individual experiments investigating aberrant brain activity in UD and replication problems across previous neuroimaging meta-analyses. For individual experiments, these inconsistencies may relate to use of uncorrected inference procedures, differences in experimental design and contrasts, or heterogeneous clinical populations; meta-analytically, differences may be attributable to varying inclusion and exclusion criteria or rather liberal statistical inference approaches.
Background: Recent research suggests using an imaginary version of the Timed Up and Go test (TUG) for a first assessment of cognitive impairment. By using the time difference between a real (TUGr) and an imagined (TUGi) TUG task, the objective of this study was to examine the effect of cognitive impairment on motor imagery ability. Methods: Fifty-two participants (mean age 69.3 ± 4.0 years) with mild cognitive impairment or subjective cognitive impairment were included in this study. The time difference between the TUGr and the TUGi was used as the main outcome. The Trail Making Test part B (TMT B), the ratio between TMT A and TMT B, and the Montreal Cognitive Assessment (MoCA) battery were the main independent variables. Results: The difference between TUGr and TUGi performance time and the TMT B performance time increased with decreasing cognitive function (p < 0.01). There was no relationship between TUGr and TUGi performance time and TMT B/A ratio. There were significant correlations between TUG time differences and the MoCA score (r = -0.489, p < 0.01), the TMT B (r = 0.364, p < 0.01), and the TMT B/A ratio (r = 0.377, p < 0.01). Conclusion: The combination of TUGr and TUGi may have added value in assessing cognitive impairment, which is a possible pre-stage of dementia. (PsycINFO Database Record (c) 2018 APA, all rights reserved)
Informational cues such as the price of a wine can trigger expectations about its taste quality and thereby modulate the sensory experience on a reported and neural level. Yet it is unclear how the brain translates such expectations into sensory pleasantness. We used a whole-brain multilevel mediation approach with healthy participants who tasted identical wines cued with different prices while their brains were scanned using fMRI. We found that the brain's valuation system (BVS) in concert with the anterior prefrontal cortex played a key role in implementing the effect of price cues on taste pleasantness ratings. The sensitivity of the BVS to monetary rewards outside the taste domain moderated the strength of these effects. These findings provide novel evidence for the fundamental role that neural pathways linked to motivation and affective regulation play for the effect of informational cues on sensory experiences.
Women are known to have stronger prosocial preferences than men, but it remains an open question as to how these behavioural differences arise from differences in brain functioning. Here, we provide a neurobiological account for the hypothesized gender difference. In a pharmacological study and an independent neuroimaging study, we tested the hypothesis that the neural reward system encodes the value of sharing money with others more strongly in women than in men. In the pharmacological study, we reduced receptor type-specific actions of dopamine, a neurotransmitter related to reward processing, which resulted in more selfish decisions in women and more prosocial decisions in men. Converging findings from an independent neuroimaging study revealed gender-related activity in neural reward circuits during prosocial decisions. Thus, the neural reward system appears to be more sensitive to prosocial rewards in women than in men, providing a neurobiological account for why women often behave more prosocially than men.
Background Current neuroimaging perspectives on a variety of mental disorders emphasize dysfunction of the amygdala. The neuropeptide oxytocin (OXT), a key mediator in the regulation of social cognition and behavior, accumulates in cerebrospinal fluid after intranasal administration in macaques and humans and modulates amygdala reactivity in both species. However, the translation of neuromodulatory OXT effects to novel treatment approaches is hampered by the absence of studies defining the most effective dose and dose–response latency for targeting the amygdala. Methods To address this highly relevant issue, a total of 116 healthy men underwent functional magnetic resonance imaging using a randomized, double-blind, placebo-controlled crossover study design. The experimental rationale was to systematically vary dose–test latencies (15–40, 45–70, and 75–100 minutes) and doses of OXT (12, 24, and 48 international units) in order to identify the most robust effects on amygdala reactivity. During functional magnetic resonance imaging, subjects completed an emotional face recognition task including stimuli with varying intensities ranging from low (highly ambiguous) to high (less ambiguous). Results Our results indicate that the OXT-induced inhibition of amygdala responses to fear was most effective in a time window between 45 and 70 minutes after administration of a dose of 24 international units. Furthermore, the observed effect was most evident in subjects scoring high on measures of autistic-like traits. Behavioral response patterns suggest that OXT specifically reduced an emotional bias in the perception of ambiguous faces. Conclusions These findings provide initial evidence of the most effective dose and dose–test interval for future experimental or therapeutic regimens aimed at targeting amygdala functioning using intranasal OXT administration.
Generosity is an important behavior enriching human society and can be observed across cultures. However, generosity has been shown to be modulated as a function of social distance, also referred to as social discounting. Oxytocin and empathy are other factors that have been shown to play an important role in generous behavior. However, how exactly oxytocin and empathy impact social discounting is yet unknown. Here, we administered oxytocin or placebo in a double-blind design, and measured social discounting behavior. Additionally, individual differences in empathy were assessed. Our results show that the effect of oxytocin on generous behavior is modulated by trait empathy; only for those subjects who received oxytocin there was a positive correlation between individual trait empathy and their generous behavior towards close others.
When it comes to lies, the beneficiaries of one's dishonesty play an important role in the decision-making process. Altruistic lies that are made with the intention of benefiting others are a specific type of lies and very common in real life. While it has been shown that altruistic goals influence (dis)honest behaviors, the neural substrates of this effect is still unknown. To reveal how the brain integrates altruistic goals into (dis)honest decisions, this study used functional magnetic resonance imaging to examine the neural activity of participants in a real incentivized context while they were making (dis)honest decisions. We manipulated the beneficiaries of individuals' decisions (self vs. a charity) and whether the choices of higher payoffs involved deception or not. While finding that participants lied more often to benefit charities than for themselves, we observed that the altruistic goal of benefiting a charity, compared with the self-serving goal, reduced the activity in the anterior insula (AI) when lying to achieve higher payoffs. Furthermore, the degree of altruistic goal-induced reduction of AI activity was positively correlated with the degree of altruistic goal-induced reduction of honesty concerns. These results suggest that the AI serves as a neural hub in modulating the effect of altruistic goals on deception, which shed light on the underlying neural mechanism of altruistic lies.
Effective regulation of negative affective states has been associated with mental health. Impaired regulation of negative affect represents a risk factor for dysfunctional coping mechanisms such as drug use and thus could contribute to the initiation and development of problematic substance use. This study investigated behavioral and neural indices of emotion regulation in regular marijuana users (n = 23) and demographically matched nonusing controls (n = 20) by means of an fMRI cognitive emotion regulation (reappraisal) paradigm. Relative to nonusing controls, marijuana users demonstrated increased neural activity in a bilateral frontal network comprising precentral, middle cingulate, and supplementary motor regions during reappraisal of negative affect (P < 0.05, FWE) and impaired emotion regulation success on the behavioral level (P < 0.05). Amygdala-focused analyses further revealed impaired amygdala downregulation in the context of decreased amygdala–dorsolateral prefrontal cortex functional connectivity (P < 0.05, FWE) during reappraisal in marijuana users relative to controls. Together, the present findings could reflect an unsuccessful attempt of compensatory recruitment of additional neural resources in the context of disrupted amygdala–prefrontal interaction during volitional emotion regulation in marijuana users. As such, impaired volitional regulation of negative affect might represent a consequence of, or risk factor for, regular marijuana use. Hum Brain Mapp 38:4270–4279, 2017.
2016
Leadership mechanisms provide a potential means to mitigate social dilemmas, but empirical evidence on the success of such mechanisms is mixed. In this paper, we explore the institutional frame as a relevant factor for the effectiveness of leadership. We compare subjects’ behavior in public-goods experiments that are either framed positively (give-some game) or negatively (take-some game). We observe that leader and follower decisions are sensitive to the institutional frame. Leaders contribute less in the take-some game, and the correlation between leaders’ and followers’ contribution is weaker in the take-some game. Additionally, using a strategy method to elicit followers’ reactions at the individual level, we find evidence for the malleability of followers’ revealed cooperation types. Taken together, the leadership institution is found to be less efficient in the take- than in the give-frame, both in games that are played only once and repeatedly.
SignificanceLysergic acid diethylamide (LSD), the prototypical "psychedelic," may be unique among psychoactive substances. In the decades that followed its discovery, the magnitude of its effect on science, the arts, and society was unprecedented. LSD produces profound, sometimes life-changing experiences in microgram doses, making it a particularly powerful scientific tool. Here we sought to examine its effects on brain activity, using cutting-edge and complementary neuroimaging techniques in the first modern neuroimaging study of LSD. Results revealed marked changes in brain blood flow, electrical activity, and network communication patterns that correlated strongly with the drugs hallucinatory and other consciousness-altering properties. These results have implications for the neurobiology of consciousness and for potential applications of LSD in psychological research. Lysergic acid diethylamide (LSD) is the prototypical psychedelic drug, but its effects on the human brain have never been studied before with modern neuroimaging. Here, three complementary neuroimaging techniques: arterial spin labeling (ASL), blood oxygen level-dependent (BOLD) measures, and magnetoencephalography (MEG), implemented during resting state conditions, revealed marked changes in brain activity after LSD that correlated strongly with its characteristic psychological effects. Increased visual cortex cerebral blood flow (CBF), decreased visual cortex alpha power, and a greatly expanded primary visual cortex (V1) functional connectivity profile correlated strongly with ratings of visual hallucinations, implying that intrinsic brain activity exerts greater influence on visual processing in the psychedelic state, thereby defining its hallucinatory quality. LSDs marked effects on the visual cortex did not significantly correlate with the drugs other characteristic effects on consciousness, however. Rather, decreased connectivity between the parahippocampus and retrosplenial cortex (RSC) correlated strongly with ratings of "ego-dissolution" and "altered meaning," implying the importance of this particular circuit for the maintenance of "self" or "ego" and its processing of "meaning." Strong relationships were also found between the different imaging metrics, enabling firmer inferences to be made about their functional significance. This uniquely comprehensive examination of the LSD state represents an important advance in scientific research with psychedelic drugs at a time of growing interest in their scientific and therapeutic value. The present results contribute important new insights into the characteristic hallucinatory and consciousness-altering properties of psychedelics that inform on how they can model certain pathological states and potentially treat others.
The sense of agency describes the ability to experience oneself as the agent of one's own actions. Previous studies of the sense of agency manipulated the predicted sensory feedback related either to movement execution or to the movement's outcome, for example by delaying the movement of a virtual hand or the onset of a tone that resulted from a button press. Such temporal sensorimotor discrepancies reduce the sense of agency. It remains unclear whether movement-related feedback is processed differently than outcome-related feedback in terms of agency experience, especially if these types of feedback differ with respect to sensory modality. We employed a mixed-reality setup, in which participants tracked their finger movements by means of a virtual hand. They performed a single tap, which elicited a sound. The temporal contingency between the participants' finger movements and (i) the movement of the virtual hand or (ii) the expected auditory outcome was systematically varied. In a visual control experiment, the tap elicited a visual outcome. For each feedback type and participant, changes in the sense of agency were quantified using a forced-choice paradigm and the Method of Constant Stimuli. Participants were more sensitive to delays of outcome than to delays of movement execution. This effect was very similar for visual or auditory outcome delays. Our results indicate different contributions of movement- versus outcome-related sensory feedback to the sense of agency, irrespective of the modality of the outcome. We propose that this differential sensitivity reflects the behavioral importance of assessing authorship of the outcome of an action.
Mirror neurons (MNs) are considered to be the supporting neural mechanism for action understanding. MNs have been identified in monkey’s area F5. The identification of MNs in the human homolog of monkeys’ area F5 Broadmann Area 44/45 (BA 44/45) has been proven methodologically difficult. Cross-modal functional MRI (fMRI) adaptation studies supporting the existence of MNs restricted their analysis to a priori candidate regions, whereas studies that failed to find evidence used non-object-directed (NDA) actions. We tackled these limitations by using object-directed actions (ODAs) differing only in terms of their object directedness in combination with a cross-modal adaptation paradigm and a whole-brain analysis. Additionally, we tested voxels’ blood oxygenation level-dependent (BOLD) response patterns for several properties previously reported as typical MN response properties. Our results revealed 52 voxels in left inferior frontal gyrus (IFG; particularly BA 44/45), which respond to both motor and visual stimulation and exhibit cross-modal adaptation between the execution and observation of the same action. These results demonstrate that part of human IFG, specifically BA 44/45, has BOLD response characteristics very similar to monkey’s area F5.
Several lines of evidence have shown that idiosyncratic facial movements can convey information about identity in addition to facial form (Hill & Johnston, 2001; Knappmeyer, Thornton, & Bülthoff, 2003; Lander, Chuang, & Wickham, 2006; Rosenblum et al., 2002), yet the exact role of facial motion as a cue for identity is still unclear (O’Toole, Roark, & Abdi, 2002). In particular, it is not known which facial movements are idiosyncratic, and how efficiently the face perception system extracts identity information from these facial movements. Here, we hypothesize that the amount of identity information and humans’ sensitivity to this information varies with the type of facial movement. First, we assessed human observers’ sensitivity to identity information in different types of facial movements. To this end, we recorded four different actors performing facial movements in three social contexts: (1) emotional (e.g., anger), (2) emotional in a social interaction (e.g., being angry at someone) and (3) social interaction (e.g., saying goodbye to someone). To separate form from motion cues, we used a recent facial motion capture and animation system (Dobs et al., 2014) and animated a single avatar head with the recorded nonrigid facial movements from these four actors. Using a delayed matching-to-sample task, we tested in which context human observers can match the identity of unfamiliar actors based only on their facial motion. Observers were able to match the identity across emotional facial movements occurring in a social interaction, but not across basic emotional facial expressions. Sensitivity was highest across non-emotional, speech-related movements occurring in a social interaction. Second, we quantified spatio-temporal information (e.g., amount of eyebrow raise) of the recorded facial movements and built model observers processing this measure. These model observers showed higher sensitivity than our human observers, but importantly, they showed the same pattern of performance across contexts. Thus, our findings reveal (i) that human observers cannot recognize unfamiliar persons from the way they perform basic emotional facial expressions even though these expressions do contain some identity information, and (ii) that such recognition is possible from conversational and speech-related movements which contain more identity 51 information. We hypothesize that these differences are due to the constraints under which these movements are executed: basic emotions are performed quite stereotypically, whereas conversational and speech-related movements are performed more idiosyncratically.
Purpose Semi-quantitative analysis of hippocampal internal architecture (HIA) on MRI has been shown to be a reliable predictor of the side of seizure onset in patients with temporal lobe epilepsy (TLE). In the present study, we investigated the relationship between postoperative seizure outcome and preoperative semi-quantitative measures of HIA. Methods We determined HIA on high in-plane resolution preoperative T2 short tau inversion recovery MR images in 79 patients with presumed unilateral mesial TLE (mTLE) due to hippocampal sclerosis (HS) who underwent amygdalohippocampectomy and postoperative follow up. HIA was investigated with respect to postoperative seizure freedom, neuronal density determined from resected hippocampal specimens, and conventionally acquired hippocampal volume. Results HIA ratings were significantly related to some neuropathological features of the resected hippocampus (e.g. neuronal density of selective CA regions, Wyler grades), and bilaterally with preoperative hippocampal volume. However, there were no significant differences in HIA ratings of the to-be-resected or contralateral hippocampus between patients rendered seizure free (ILAE 1) compared to those continuing to experience seizures (ILAE 2-5). Conclusions This work indicates that semi-quantitative assessment of HIA on high-resolution MRI provides a surrogate marker of underlying histopathology, but cannot prospectively distinguish between patients who will continue to experience postoperative seizures and those who will be rendered seizure free. The predictive power of HIA for postoperative seizure outcome in non-lesional patients with TLE should be explored.
The rate of patients with obesity has been rapidly increasing, and this imposes a heavy economic burden on health-care systems. Food decisions, under the influence of different internal and external factors, lie at the core of this increasing health problem. Due to the biological necessity to consume sufficient amounts of food and to correctly regulate energy expenditure, there are different systems that control food intake. This article first focuses on neurobiological and hormonal foundations and explains various metabolic short- and long-term signals, such as leptin, insulin, and ghrelin. We then also present genetic factors, which directly or indirectly (via other genes or environmental influences) may affect nutritional status. Since the consumption of high-caloric foods is accompanied by dopamine release and the activation of the brain's reward system, we will then present the interdependence of metabolic and reward systems. Last, we will present a neuroeconomic perspective that complements research on metabolic and hedonic feeding regulation.
Every day, people struggle to make healthy eating decisions. Nutrition labels have been used to help people properly balance the tradeoff between healthiness and taste, but research suggests that these labels vary in their effectiveness. Here, we investigated the cognitive mechanism underlying value-based decisions with nutrition labels as modulators of value. More specifically, we used a binary decision task between products along with two different nutrition labels to examine how salient, color-coded labels, compared to purely information-based labels, alter the choice process. Using drift-diffusion modeling, we investigated whether color-coded labels alter the valuation process, or whether they induce a simple stimulus- response association consistent with the traffic-light colors irrespective of the features of the item, which would manifest in a starting point bias in the model. We show that color-coded labels significantly increased healthy choices by increasing the rate of preference formation (drift rate) towards healthier options without altering the starting point. Salient labels increased the sensitivity to health and decreased the weight on taste, indicating that the integration of health and taste attributes during the choice process is sensitive to how information is displayed. Salient labels proved to be more effective in altering the valuation process towards healthier, goal-directed decisions.
Congenital prosopagnosia, the innate impairment in recognizing faces, is a very heterogeneousdisorder with different phenotypical manifestations. To investigate the nature of prosopagnosia inmore detail, we tested 16 prosopagnosics and 21 controls with an extended test batteryaddressing various aspects of face recognition. Our results show that prosopagnosics exhibitedsignificant impairments in several face recognition tasks: impaired holistic processing (they weretested amongst others with the Cambridge Face Memory Test (CFMT)) as well as reducedprocessing of configural information of faces. This test battery also revealed some new findings.While controls recognized moving faces better than static faces, prosopagnosics did not exhibitthis effect. Furthermore, prosopagnosics had significantly impaired gender recognition—which isshown on a groupwise level for the first time in our study. There was no difference betweengroups in the automatic extraction of face identity information or in object recognition as testedwith the Cambridge Car Memory Test. In addition, a methodological analysis of the tests revealedreduced reliability for holistic face processing tests in prosopagnosics. To our knowledge, this isthe first study to show that prosopagnosics showed a significantly reduced reliability coefficient(Cronbach’s alpha) in the CFMT compared to the controls. We suggest that compensatory strategies employed by the prosopagnosics might be the cause for the vast variety of responsepatterns revealed by the reduced test reliability. This finding raises the question whether classicalface tests measure the same perceptual processes in controls and prosopagnosics.
Das Miteinander im akademi- schen Alltag ist nicht immer von Harmonie geprägt. Nicht selten kommt es zu Gefühlen von Ärger und Frust, beispielsweise bei der Begutachtung einer Publi- kation oder bei sonstigen Behandlungen, die als unfair erlebt werden. Welche Folgen können diese Emotionen haben und wie geht man am besten damit um? Ergebnisse einer neuen Studie.
Humans display an intriguing propensity to help the victim of social norm violations or punish the violators which require theory-of-mind (ToM)/mentalizing abilities. The hypothalamic peptide oxytocin (OXT) has been implicated in modulating various pro-social behaviors/perception including trust, cooperation, and empathy. However, it is still elusive whether OXT also influences neural responses during third-party altruistic decisions, especially in ToM-related brain regions such as the temporo-parietal junction (TPJ). To address this question, we conducted a pharmacological functional magnetic resonance imaging experiment with healthy male participants in a randomized, double-blind, cross-over design. After the intranasal administration synthetic OXT (OXT(IN)) or placebo (PLC), participants could transfer money from their own endowment to either punish a norm violator or help the victim. In some trials, participants observed the decisions made by a computer. Behaviorally, participants under OXT(IN) showed a trend to accelerate altruistic decisions. At the neural level, we observed a strong three-way interaction between drug treatment (OXT/PLC), agency (self/computer), and decision (help/punish), such that OXT(IN) selectively enhanced activity in the left TPJ during observations of others being helped by the computer. Collectively, our findings indicate that OXT enhances prosocial-relevant perception by increasing ToM-related neural activations.
People differ in the way they approach and handle choices with unsure outcomes. In this study, we demonstrate that individual differences in the neural processing of gains and losses relates to attentional differences in the way individuals search for information in gambles. Fifty subjects participated in two independent experiments. Participants first completed an fMRI experiment involving financial gains and losses. Subsequently, they performed an eye-tracking experiment on binary choices between risky gambles, each displaying monetary outcomes and their respective probabilities. We find that individual differences in gain and loss processing relate to attention distribution. Individuals with a stronger reaction to gains in the ventromedial prefrontal cortex paid more attention to monetary amounts, while a stronger reaction in the ventral striatum to losses was correlated with an increased attention to probabilities. Reaction in the posterior cingulate cortex to losses was also found to correlate with an increased attention to probabilities. Our data show that individual differences in brain activity and differences in information search processes are closely linked.
Introduction Nicotine and methylphenidate are putative cognitive enhancers in healthy and patient populations. Although they stimulate different neurotransmitter systems, they have been shown to enhance performance on overlapping measures of attention. So far, there has been no direct comparison of the effects of these two stimulants on behavioural performance or brain function in healthy humans. Here, we directly compare the two compounds using a well-established oculomotor biomarker in order to explore common and distinct behavioural and neural effects. Methods Eighty-two healthy male non-smokers performed a smooth pursuit eye movement task while lying in an fMRI scanner. In a between-subjects, double-blind design, subjects either received placebo (placebo patch and capsule), nicotine (7 mg nicotine patch and placebo capsule), or methylphenidate (placebo patch and 40 mg methylphenidate capsule). Results There were no significant drug effects on behavioural measures. At the neural level, methylphenidate elicited higher activation in left frontal eye field compared to nicotine, with an intermediate response under placebo. Discussion The reduced activation of task-related regions under nicotine could be associated with more efficient neural processing, while increased hemodynamic response under methylphenidate is interpretable as enhanced processing of task-relevant networks. Together, these findings suggest dissociable neural effects of these putative cognitive enhancers.
The SNARC effect refers to an association of numbers and spatial properties of responses that is commonly thought to be amodal and independent of stimulus notation. We tested for a horizontal SNARC effect using Arabic digits, simple-form Chinese characters and Chinese hand signs in participants from Mainland China. We found a horizontal SNARC effect in all notations. This is the first time that a horizontal SNARC effect has been demonstrated in Chinese characters and Chinese hand signs. We tested for the SNARC effect in two experiments (parity judgement and magnitude judgement). The parity judgement task yielded clear, consistent SNARC effects in all notations, whereas results were more mixed in magnitude judgement. Both Chinese characters and Chinese hand signs are represented non-symbolically for low numbers and symbolically for higher numbers, allowing us to contrast within the same notation the effects of heavily learned non-symbolic vs. symbolic representation on the processing of numbers. In addition to finding a horizontal SNARC effect, we also found a robust numerical distance effect in all notations. This is particularly interesting as it persisted when participants reported using purely visual features to solve the task, thereby suggesting that numbers were processed semantically even when the task could be solved without the semantic information.
Loss aversion is a decision bias, reflecting a greater sensitivity to losses than to gains in a decision situation. Recent neuroscientific research has shown that mesocorticolimbic structures like ventromedial prefrontal cortex and the ventral striatum constitute a bidirectional neural system that processes gains and losses and exhibits a neural basis of loss aversion. On a functional and structural level, the amygdala and insula also seem to play an important role in the processing of loss averse behavior. By applying voxel-based morphometry to structural brain images in N = 41 healthy participants, the current study provides further evidence for the relationship of brain structure and loss aversion. The results show a negative correlation of gray matter volume in bilateral posterior insula as well as left medial frontal gyrus with individual loss aversion. Hence, higher loss aversion is associated with lower gray matter volume in these brain areas. Both structures have been discussed to play important roles in the brain's salience network, where the posterior insula is involved in interoception and the detection of salience. The medial frontal gyrus might impact decision making through its dense connections with the anterior cingulate cortex. A possible explanation for the present finding is that structural differences in these regions alter the processing of losses and salience, possibly biasing decision making towards avoidance of negative outcomes.
The brain is an intricate network, not only structur-ally but also functionally. On the functional level, connectivity in the brain is organized in separable yet interacting networks that support information processing by maintaining a ready state, even in the absence of external stimulation. It has been hypothesized that an insular-opercular network underlies the processing of emotionally salient information and that indi-vidual differences in functional connectivity within this net-work correspond to individual differences in trait anxiety. Here, we tested this relationship by applying graph analysis to multiple regions of interests delineating the insular-opercular network to estimate the characteristic path length that quantifies the overall information exchange efficiency within a given network. We found that people scoring high on the anxiety-related temperament-dimension harm avoid-ance had decreased insular-opercular network efficiency in the resting state, as indicated by a higher characteristic path length. Furthermore, people scoring high on harm avoidance showed generally reduced functional connectivity between brain regions; the relationship between harm avoidance and insular-opercular network efficiency remained significant when controlling for mean connectivity within this network. No such results were found for other resting-state networks. The results provide insights into how personality is organized in the human brain and point toward clinically relevant endophenotypes for affective and mood disorders.
The brain is an intricate network, not only structurally but also functionally. On the functional level, connectivity in the brain is organized in separable yet interacting networks that support information processing by maintaining a ready state, even in the absence of external stimulation. It has been hypothesized that an insular-opercular network underlies the processing of emotionally salient information and that individual differences in functional connectivity within this network correspond to individual differences in trait anxiety. Here, we tested this relationship by applying graph analysis to multiple regions of interests delineating the insular-opercular network to estimate the characteristic path length that quantifies the overall information exchange efficiency within a given network. We found that people scoring high on the anxiety-related temperament-dimension harm avoidance had decreased insular-opercular network efficiency in the resting state, as indicated by a higher characteristic path length. Furthermore, people scoring high on harm avoidance showed generally reduced functional connectivity between brain regions; the relationship between harm avoidance and insular-opercular network efficiency remained significant when controlling for mean connectivity within this network. No such results were found for other resting-state networks. The results provide insights into how personality is organized in the human brain and point toward clinically relevant endophenotypes for affective and mood disorders.
One major goal in decision neuroscience is to investigate the neuronal mechanisms being responsible for the computation of product preferences. The aim of the present fMRI study was to investigate whether similar patterns of brain activity, reflecting category dependent and category independent preference signals, can be observed in case of different food product categories (i.e. chocolate bars and salty snacks). To that end we used a multivariate searchlight approach in which a linear support vector machine (l-SVM) was trained to distinguish preferred from non-preferred chocolate bars and subsequently tested its predictive power in case of chocolate bars (within category prediction) and salty snacks (across category prediction). Preferences were measured by a binary forced choice decision paradigm before the fMRI task. In the scanner, subjects saw only one product per trial which they had to rate after presentation. Consistent with previous multi voxel pattern analysis (MVPA) studies, we found category dependent preference signals in the ventral parts of medial prefrontal cortex (mPFC), but also in dorsal anterior cingulate cortex (dACC) and dorsolateral prefrontal cortex (dlPFC). Category independent preference signals were observed in the dorsal parts of mPFC, dACC, and dlPFC. While the first two results have also been reported in a closely related study, the activation in dlPFC is new in this context. We propose that the dlPFC activity does not reflect the products’ value computation per se, but rather a modulatory signal which is computed in anticipation of the forthcoming product rating after stimulus presentation. Furthermore we postulate that this kind of dlPFC activation emerges only if the anticipated choices fall into the domain of primary rewards, such as foods. Thus, in contrast to previous studies which investigated preference decoding for stimuli from utterly different categories, the present study revealed some food domain specific aspects of preference processing in the human brain.
Mirror neurons (MNs) are considered to be the supporting neural mechanism for action understanding. MNs have been identified in monkey’s area F5. The identification of MNs in the human homolog of monkeys’ area F5 Broadmann Area 44/45 (BA 44/45) has been proven methodologically difficult. Cross-modal functional MRI (fMRI) adaptation studies supporting the existence of MNs restricted their analysis to a priori candidate regions, whereas studies that failed to find evidence used non-object-directed (NDA) actions. We tackled these limitations by using object-directed actions (ODAs) differing only in terms of their object directedness in combination with a cross-modal adaptation paradigm and a whole-brain analysis. Additionally, we tested voxels’ blood oxygenation level-dependent (BOLD) response patterns for several properties previously reported as typical MN response properties. Our results revealed 52 voxels in left inferior frontal gyrus (IFG; particularly BA 44/45), which respond to both motor and visual stimulation and exhibit cross-modal adaptation between the execution and observation of the same action. These results demonstrate that part of human IFG, specifically BA 44/45, has BOLD response characteristics very similar to monkey’s area F5.
We measured how well perception of color saturation in natural scenes can be predicted by different measures that are available in the literature. We presented 80 color images of natural scenes or their gray-scale counterparts to our observers, who were asked to choose the pixel from each image that appeared to be the most saturated. We compared our observers’ choices to the predictions of seven popular saturation measures. For the color images, all of the measures predicted perception of saturation quite well, with CIECAM02 performing best. Differences between the measures were small but systematic. When gray-scale images were viewed, observers still chose pixels whose counterparts in the color images were saturated above average. This indicates that image structure and prior knowledge can be relevant to perception of saturation. Nevertheless, our results also show that saturation in natural scenes can be specified quite well without taking these factors into account.
The most prominent explanation for the spatial numerical association of response codes (SNARC) effect is the direct mapping account (DMA). The DMA assumes that (a) numbers are represented on a mental number line, (b) this mental number line is mapped to external space, and (c) the better the mapping location corresponds to the response location, the faster the response. The DMA leaves open whether a variation of response locations can (ceteris paribus) influence the location to which numbers are mapped in external space. In order to investigate this question, we varied response key distance during a standard parity judgment and a magnitude judgment task. We found that even drastic manipulations of response key distance did not modulate the SNARC effect. Power and meta-analyses show that this null effect is not due to insufficient statistical power or a poor experimental setup. Thus, our results indicate that, in order for the DMA to explain the SNARC effect, it must assume that the mapping from the mental number line to external space is anchored to response location. For future research, our results suggest that it is not necessary to control the horizontal separation of the response keys in basic SNARC experiments.
Clinical as well as epidemiological studies indicate that chronic somatic diseases are often accompanied by mental disorders. Although an early and correct recognition of the psychosomatic comorbidity has important implications for therapy and the course of the whole disease pattern, this occurs only in a limited number of cases. Notably, the timely diagnosis and treatment of the comorbid mental disorder can lead to an alleviation of its symptoms and significant enhancement of the quality of life for the double burden patients.
The uncompetitive NMDA receptor antagonist ketamine has been proposed to model symptoms of psychosis. Smooth pursuit eye movements (SPEM) are an established biomarker of schizophrenia. SPEM performance has been shown to be impaired in the schizophrenia spectrum and during ketamine administration in healthy volunteers. However, the neural mechanisms mediating SPEM impairments during ketamine administration are unknown. In a counter-balanced, placebo-controlled, double-blind, within-subjects design, 27 healthy participants received intravenous racemic ketamine (100 ng/mL target plasma concentration) on one of two assessment days and placebo (intravenous saline) on the other. Participants performed a block-design SPEM task during functional magnetic resonance imaging (fMRI) at 3 Tesla field strength. Self-ratings of psychosis-like experiences were obtained using the Psychotomimetic States Inventory (PSI). Ketamine administration induced psychosis-like symptoms, during ketamine infusion, participants showed increased ratings on the PSI dimensions cognitive disorganization, delusional thinking, perceptual distortion and mania. Ketamine led to robust deficits in SPEM performance, which were accompanied by reduced blood oxygen level dependent (BOLD) signal in the SPEM network including primary visual cortex, area V5 and the right frontal eye field (FEF), compared to placebo. A measure of connectivity with V5 and FEF as seed regions, however, was not significantly affected by ketamine. These results are similar to the deviations found in schizophrenia patients. Our findings support the role of glutamate dysfunction in impaired smooth pursuit performance and the use of ketamine as a pharmacological model of psychosis, especially when combined with oculomotor biomarkers.
Humans are tremendously sensitive to unfairness. Unfairness provokes strong negative emotional reactions and influences our subsequent decision making. These decisions might not only have consequences for ourselves and the person who treated us unfairly but can even transmit to innocent third persons - a phenomenon that has been referred to as generalized negative reciprocity. In this study we aimed to investigate whether regulation of emotions can interrupt this chain of unfairness. Real allocations in a dictator game were used to create unfair situations. Three different regulation strategies, namely writing a message to the dictator who made an unfair offer, either forwarded or not forwarded, describing a neutral picture and a control condition in which subjects just had to wait for three minutes, were then tested on their ability to influence the elicited emotions. Subsequently participants were asked to allocate money between themselves and a third person. We show that writing a message which is forwarded to the unfair actor is an effective emotion regulation strategy and that those participants who regulated their emotions successfully by writing a message made higher allocations to a third person. Thus, using message writing as an emotion regulation strategy can interrupt the chain of unfairness.
The antisaccade task is a prominent tool to investigate the response inhibition component of cognitive control. Recent theoretical accounts explain performance in terms of parallel programming of exogenous and endogenous saccades, linked to the horse race metaphor. Previous studies have tested the hypothesis of competing saccade signals at the behavioral level by selectively slowing the programming of endogenous or exogenous processes e.g. by manipulating the probability of antisaccades in an experimental block. To gain a better understanding of inhibitory control processes in parallel saccade programming, we analyzed task-related eye movements and blood oxygenation level dependent (BOLD) responses obtained using functional magnetic resonance imaging (fMRI) at 3T from 16 healthy participants in a mixed antisaccade and prosaccade task. The frequency of antisaccade trials was manipulated across blocks of high (75%) and low (25%) antisaccade frequency. In blocks with high antisaccade frequency, antisaccade latencies were shorter and error rates lower whilst prosaccade latencies were longer and error rates were higher. At the level of BOLD, activations in the task-related saccade network (left inferior parietal lobe, right inferior parietal sulcus, left precentral gyrus reaching into left middle frontal gyrus and inferior frontal junction) and deactivations in components of the default mode network (bilateral temporal cortex, ventromedial prefrontal cortex) compensated increased cognitive control demands. These findings illustrate context dependent mechanisms underlying the coordination of competing decision signals in volitional gaze control.
OBJECTIVE: Autoantibodies against glutamic acid decarboxylase (GAD) and the voltage-gated potassium channel (VGKC) complex are associated with distinct subtypes of limbic encephalitis regarding clinical presentation, response to therapy, and outcome. The aim of this study was to investigate white matter changes in these two limbic encephalitis subtypes by means of diffusion tensor imaging (DTI).\n\nMETHODS: Diffusion data were obtained in 14 patients with GAD antibodies and 16 patients with VGKC-complex antibodies and compared with age- and gender-matched control groups. Voxelwise statistical analysis was carried out using tract-based spatial statistics. The results were furthermore compared with those of 15 patients with unilateral histologically confirmed hippocampal sclerosis and correlated with verbal and figural memory performance.\n\nRESULTS: We found widespread changes of fractional anisotropy and all diffusivity parameters in GAD-associated limbic encephalitis, whereas no changes were found in VGKC-complex-associated limbic encephalitis. The changes observed in the GAD group were even more extensive when compared against those of the hippocampal sclerosis group, although the disease duration was markedly shorter in patients with GAD antibodies. Correlation analysis revealed areas with a trend toward a negative correlation of diffusivity parameters with figural memory performance located mainly in the right temporal lobe in the GAD group as well.\n\nSIGNIFICANCE: The present study provides further evidence that, depending on the associated antibody, limbic encephalitis features clearly distinct imaging characteristics by showing widespread white matter changes in GAD-associated limbic encephalitis and preserved white matter integrity in VGKC-complex-associated limbic encephalitis. Furthermore, our results contribute to a better understanding of the specific pathophysiologic properties in these two subforms of limbic encephalitis by revealing that patients with GAD antibodies show widespread affections of white matter across various regions of the brain. In contrast to this, the inflammatory process seems to be more localized in VGKC-complex-associated limbic encephalitis, primarily affecting mesiotemporal gray matter.
The somewhat contra-intuitive success of PWYW has sparked a great deal of behavioral work on economical decision making in PWYW contexts in the past. Empirical studies on the neural basis of PWYW decisions, however, are scarce. In the present paper, we present an experimental protocol to study PWYW decision making while simultaneously acquiring functional magnetic resonance imaging data. Participants have the possibility to buy music either under a traditional “fixed-price” (FP) condition or in a condition that allows them to freely decide on the price. The behavioral data from our experiment replicate previous results on the general feasibility of the PWYW mechanism. On the neural level, we observe distinct differences between the two conditions: In the FP- condition, neural activity in frontal areas during decision-making correlates positively with the participants’ willingness to pay. No such relationship was observed under PWYW conditions in any neural structure. Directly comparing neural activity during PWYW and the FP-condition we observed stronger activity of the lingual gyrus during PWYW decisions. Results demonstrate the usability of our experimental paradigm for future investigations into PWYW decision-making and provides first insights into neural mechanisms during self-determined pricing decisions.
Can beneficial ends justify morally questionable means? To investigate how monetary outcomes influence the neural responses to lying, we used a modified, cheap talk sender-receiver game in which participants were the direct recipients of lies and truthful statements resulting in either beneficial or harmful monetary outcomes. Both truth-telling (versus lying) as well as beneficial (versus harmful) outcomes elicited higher activity in the nucleus accumbens (NAcc). Lying (versus truth-telling) elicited higher activity in the supplementary motor area (SMA), right inferior frontal gyrus (IFG), superior temporal sulcus (STS), and left anterior insula (AI). Moreover, the significant interaction effect was found in the left amygdala, which showed that the monetary outcomes modulated the neural activity in the left amygdala only when truth-telling rather than lying. Our study identified a neural network associated with the reception of lies and truth, including the regions linked to the reward process, recognition and emotional experiences of being treated (dis)honestly.
Many previous functional magnetic resonance imaging (fMRI) studies on deception used a paradigm of "instructed lies", which is different than other, more spontaneous forms of lying behavior. The present study aimed to investigate the neural processes underlying spontaneous and instructed lying and truth-telling, and to investigate the different mechanisms involved. This study used a modified sic bo gambling game with real payoffs in order to induce lying. In the spontaneous sessions, the participants themselves decided whether or not to lie, whereas in the instructed sessions they were explicitly told to respond either honestly or dishonestly. In the spontaneous lying (vs. truth-telling) condition, the subgenual anterior cingulate cortex (sACC) showed significantly higher activity, whereas the right dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC) and inferior parietal lobule (IPL) were more strongly activated when participants spontaneously told the truth (vs. lied). Our results suggest that the extra cognitive control required for suppressing the self-interest motives in spontaneous truth-telling is associated with higher activity in the fronto-parietal network, while the process of negative emotion in spontaneous lying induced greater involvement of the sACC. Although similar to spontaneous deception, instructed deception engenders greater involvement of the right inferior frontal gyrus (IFG), left supplementary motor area (SMA), anterior cingulate cortex (ACC), IPL and superior frontal gyrus (SFG) compared to baseline, instructed decisions did not elicit similar activation patterns in the regions of sACC, DLPFC, VLPFC and IPL which were sensitive to either spontaneous truth-telling or lying.
2015
Does probation pay a double dividend? Society saves the cost of incarceration, and convicts preserve their liberty. But does probation also reduce the risk of recidivism? In a meta-study we show that the field evidence is inconclusive. Moreover, it struggles with an identification problem: those put on probation are less likely to recidivate in the first place. We therefore complement the existing field evidence with a novel lab experiment that isolates the definitional feature of probation: the first sanction is conditional on being sanctioned again during the probation period. We find that probationers are more likely to recidivate (i.e., to reduce their contributions to a joint project), that punishment cost is higher, efficiency lower, and inequity higher. While experimental subjects are on probation, they increase their contributions to a joint project. However, once the probation period expires, they reduce their contributions. While in the aggregate these two effects almost cancel out, critically, those not punished themselves trust the institution less if punishment does not become immediately effective.
Driven by an ever-growing number of studies that explore the effectiveness of institutional mechanisms meant to mitigate cooperation problems, recent years have seen an increasing interest in the endogenous implementation of these institutions. In this paper, we test within a unified framework how the process of institution formation is affected by three key aspects of natural environments: (i) heterogeneity among players in the benefits of cooperation, (ii) (a)symmetry in players׳ institutional obligations, and (iii) potential trade-offs between efficiency and equality in payoff allocations. We observe social preferences to be limiting the scope for institution formation. Inequality-averse players frequently object to institutions that fail to address differences in players׳ benefits from cooperation – even if rejecting the institution causes monetary losses to all players. Relating our findings to previous studies on institution formation, we discuss potential advantages and drawbacks of stipulating unanimous support for implementing institutions that foster cooperation.
RATIONALE: Pharmacological and genetic modulation of cholinergic nicotinic neurotransmission influence visuospatial attention in humans. Prior studies show that nicotine as well as a single nucleotide polymorphism (SNP) in the gene coding for the alpha 4 subunit of the nicotinic acetylcholine receptor (CHRNA4) modulate visuospatial attention and distractor interference. The CHRNA4 gene synergistically interacts with a polymorphism in the dopaminergic receptor type d2 (DRD2) gene and impacts brain structure and cognition. OBJECTIVE: We aimed to investigate whether CHRNA4 and DRD2 genotypes alter the effects of nicotine on distractor interference. METHODS: Fifty-eight young healthy non-smokers were genotyped for CHRNA4 (rs1044396) and DRD2 (rs6277). They received either 7 mg transdermal nicotine or a matched placebo in a double-blind, within-subject design 1 h prior to performing a visual search task with distractors. RESULTS: In isolation, DRD2 but not CHRNA4 genotype modulated the effects of nicotine on distractor interference with DRD2 CC carriers showing the strongest reduction of distractor interference after nicotine administration. A further analysis provided additional evidence that this effect was driven by those subjects, who carried at least one C allele in the CHRNA4 gene. CONCLUSION: The effects of nicotine on distractor interference are modulated synergistically by cholinergic and dopaminergic genetic variations. Hence, both genes may contribute to the often reported individual variability in cognitive and neural effects of nicotine.
The proneness to minor errors and slips in everyday life as assessed by the Cognitive Failures Questionnaire (CFQ) constitutes a trait characteristic and is reflected in stable features of brain structure and function. It is unclear, however, how dynamic interactions of large-scale brain networks contribute to this disposition. To address this question, we performed a high model order independent component analysis (ICA) with subsequent dual regression on resting-state fMRI data from 71 subjects to extract temporal time courses describing the dynamics of 17 resting-state networks (RSN). Dynamic network interactions between all 17 RSN were assessed by linear correlations between networks' time courses. On this basis, we investigated the relationship between subject-level RSN interactions and the susceptibility to everyday cognitive failure. We found that CFQ scores were significantly correlated with the interplay of the cingulo-opercular network (CON) and a posterior parietal network which unifies clusters in the posterior cingulate, precuneus, intraparietal lobules and middle temporal regions. Specifically, a higher positive functional connectivity between these two RSN was indicative of higher proneness to cognitive failure. Both the CON and posterior parietal network are implicated in cognitive functions, such as tonic alertness and executive control. Results indicate that proper checks and balances between the two networks are needed to protect against cognitive failure. Furthermore, we demonstrate that the study of temporal network dynamics in the resting state is a feasible tool to investigate individual differences in cognitive ability and performance.
Cognitive and neuronal effects of nicotine show high interindividual variability. Recent findings indicate that genetic variations that affect the cholinergic and dopaminergic neurotransmitter system impact performance in cognitive tasks and effects of nicotine. The current pharmacogenetic functional magnetic resonance imaging (fMRI) study aimed to investigate epistasis effects of CHRNA4/DRD2 variations on behavioural and neural correlates of visuospatial attention after nicotine challenge using a data driven partial least squares discriminant analysis (PLS-DA) approach. Fifty young healthy non-smokers were genotyped for CHRNA4 (rs1044396) and DRD2 (rs6277). They received either 7 mg transdermal nicotine or a matched placebo in a double blind within subject design prior to performing a cued target detection task with valid and invalid trials. On behavioural level, the strongest benefits of nicotine in invalid trials were observed in participants carrying both, the DRD2 T- and CHRNA4 C+ variant. Neurally, we were able to demonstrate that different DRD2/CHRNA4 groups can be decoded from the pattern of brain activity in invalid trials under nicotine. Neural substrates of interindividual variability were found in a network of attention-related brain regions comprising the pulvinar, the striatum, the middle and superior frontal gyri, the insula, the left precuneus, and the right middle temporal gyrus. Our findings suggest that polymorphisms in the CHRNA4 and DRD2 genes are a relevant source of individual variability in pharmacological studies with nicotine.
Food decisions occur very frequently and are influenced by a variety of individual as well as contextual factors. Physical product attributes, including for example, caloric density, water content and sweetness are important drivers of food choice and preferences. However, food products are usually not evaluated solely based on their nutritional content. In addition, most products are packaged and carry abstract attributes, such as quality claims, and brand names. Critically, these product attributes, not products attributes also influence food consumption, reported consumption enjoyment, and product demand. A variety of these marketing actions were shown to alter consumption experiences of otherwise identical products, inducing a so-called marketing placebo effect (MPE). Here, we review studies providing insights into the various behavioral and neural processes underlying the response to these contextual marketing cues. An extensive amount of studies has shown impressive, sometimes peculiar and also disquieting effects of branding, logos, labels and prices on behavioral measures. We will illustrate the plethora of affected behaviors, ranging from increased taste pleasantness ratings for higher-priced wines to enhanced cognitive performance after drinking a higher-priced energy drink, compared to the identical lower-priced counterparts. Credence attributes, such as organic or social sustainability labels, have been gaining relevance in many industrialized countries, and influence product demand and consumption experience. We will therefore introduce studies that systematically investigated the effects of credence claims, elucidate possible mechanisms, and emphasize the negative consequences when misusing such claims. As children are an important and vulnerable target group for marketing actions, we will also specifically present studies conducted in children. These studies highlight the influence of marketing actions on children’s taste perception, product demand, and effort to obtain a certain product. We will shortly introduce the neurobiology of food choices, and present suggested processes underlying MPEs. Converging evidence confirms that MPEs are not a mere result of demand effects, but that they influence the neural responses to products down to a primary somatosensory level. We will show that marketing claims are very effective in influencing expectations and subsequent consumption experience. Therefore, we suggest that public policy interventions may build upon MPE research, and we will provide evidence for this supposition. Throughout this review, we present insights from a variety of different disciplines, including marketing, psychology, neuroscience and nutrition science. Albeit far from exhaustive, this non-systematic review aims at providing a joint perspective from various fields, highlighting that future research endeavor is certainly auspicious.
OBJECTIVE: Prevalence of obesity is high in most industrialized nations, and therefore, it is crucial to understand contextual factors underlying food choice. Nutrition labels are public policy interventions designed to adequately inform consumers about nutritional value and overall healthiness of food products. The present study examines how different nutrition labels, namely a purely information-based label (guideline daily amount, GDA) and a more explicit traffic light (TL) label, influence product valuation and choice in a functional MRI setting.\n\nMETHODS: Thirty-five healthy participants across different BMIs were instructed to valuate healthy and unhealthy food products in combination with one of the two labels and to state their willingness to pay (WTP) for the product.\n\nRESULTS: The labeling methods significantly influenced participants' WTP. Red TL signaling activated parts of the left inferior frontal gyrus/dorsolateral prefrontal cortex, a region implicated in self-control in food choice. This region, in the case of red signaling, and the posterior cingulate cortex, in the case of green signaling, showed increased coupling to the valuation system in the ventromedial prefrontal cortex.\n\nCONCLUSIONS: Our results suggest that explicitly directing attention toward nutritional values using salient nutrition labels triggers neurobiological processes that resemble those utilized by successful dieters choosing healthier products.
Value-based decision making occurs when individuals choose between different alternatives and place a value on each alternative and its attributes. Marketing actions frequently manipulate product attributes, by adding, e.g., health claims on the packaging. A previous imaging study found that an emblem for organic products increased willingness to pay (WTP) and activity in the ventral striatum (VS). The current study investigated neural and behavioral processes underlying the influence of Fair Trade (FT) labeling on food valuation and choice. Sustainability is an important product attribute for many consumers, with FT signals being one way to highlight ethically sustainable production. Forty participants valuated products in combination with an FT emblem or no emblem and stated their WTP in a bidding task while in an MRI scanner. After that, participants tasted-objectively identical-chocolates, presented either as "FT" or as "conventionally produced". In the fMRI task, WTP was significantly higher for FT products. FT labeling increased activity in regions important for reward-processing and salience, that is, in the VS, anterior and posterior cingulate, as well as superior frontal gyrus. Subjective value, that is, WTP was correlated with activity in the ventromedial prefrontal cortex (vmPFC). We find that the anterior cingulate, VS and superior frontal gyrus exhibit task-related increases in functional connectivity to the vmPFC when an FT product was evaluated. Effective connectivity analyses revealed a highly probable directed modulation of the vmPFC by those three regions, suggesting a network which alters valuation processes. We also found a significant taste-placebo effect, with higher experienced taste pleasantness and intensity for FT labeled chocolates. Our results reveal a possible neural mechanism underlying valuation processes of certified food products. The results are important in light of understanding current marketing trends as well as designing future interventions that aim at positively influencing food choice.
BACKGROUND: Food marketing research shows that child-directed marketing cues have pronounced effects on food preferences and consumption, but are most often placed on products with low nutritional quality. Effects of child-directed marketing strategies for healthy food products remain to be studied in more detail. Previous research suggests that effort provision explains additional variance in food choice. This study investigated the effects of packaging cues on explicit preferences and effort provision for healthy food items in elementary school children. Each of 179 children rated three, objectively identical, recommended yoghurt-cereal-fruit snacks presented with different packaging cues. Packaging cues included a plain label, a label focusing on health aspects of the product, and a label that additionally included unknown cartoon characters. The children were asked to state the subjective taste-pleasantness of the respective food items. We also used a novel approach to measure effort provision for food items in children, namely handgrip strength. Results show that packaging cues significantly induce a taste-placebo effect in 88% of the children, i.e., differences in taste ratings for objectively identical products. Taste ratings were highest for the child-directed product that included cartoon characters. Also, applied effort to receive the child-directed product was significantly higher. Our results confirm the positive effect of child-directed marketing strategies also for healthy snack food products. Using handgrip strength as a measure to determine the amount of effort children are willing to provide for a product may explain additional variance in food choice and might prove to be a promising additional research tool for field studies and the assessment of public policy interventions.
Breyer and Weimann (2015) suggest interpreting the results of our study on Morals and Markets (2013a,b) in “the opposite way”. In the following, we briefly discuss why this claim is unwarranted. We hope that these clarifications will help inspiring future work on causal effects of markets and other institutions on moral values.
Serotonin (5-HT) has been hypothesized to be implicated in performance monitoring by promoting behavioral inhibition in the face of aversive events. However, it is unclear whether this is restricted to external (punishment) or includes internal (response errors) events. The aim of the current study was to test whether higher 5-HT levels instigate inhibition specifically in the face of errors, measured as post-error slowing (PES), and whether this is represented in electrophysiological correlates of error processing, namely error-related negativity (ERN) and positivity. Therefore, from a large sample of human subjects (n = 878), two extreme groups were formed regarding hypothesized high and low 5-HT transporter (5-HTT) expression based on 5-HTTLPR and two additional single nucleotide polymorphisms (rs25531, rs25532). Seventeen higher (LL) and 15 lower (SS) expressing Caucasian subjects were administered the selective serotonin reuptake inhibitor (SSRI) citalopram (10 mg) intravenously in a double-blind crossover design. We found pharmacogenetic evidence for a role of 5-HT in mediating PES: SSRI administration increased PES in both genetic groups, and SS subjects displayed higher PES. These effects were absent on post-conflict slowing. However, ERN and error positivity were unaffected by pharmacogenetic factors, but ERN was decoupled from behavioral adaptation by SSRI administration in the LL group. Thus, pharmacogenetic evidence suggests that increased 5-HT levels lead to behavioral inhibition in the context of internal aversive events, but electrophysiological correlates of performance monitoring appear unrelated to the 5-HT system. Therefore, our findings are consistent with theories suggesting that 5-HT mediates the link between aversive processing and inhibition.
Social norms are a cornerstone of human society. When social norms are violated (e.g., fairness) people can either help the victim or punish the violator in order to restore justice. Recent research has shown that empathic concern influences this decision to help or punish. Using functional magnetic resonance imaging (fMRI) we investigated the neural underpinnings of third-party help and punishment and the involvement of empathic concern. Participants saw a person violating a social norm, i.e., proposing unfair offers in a dictator game, at the expense of another person. The participants could then decide to either punish the violator or help the victim. Our results revealed that both third-party helping as well as third-party punishing activated the bilateral striatum, a region strongly related with reward processing, indicating that both altruistic decisions share a common neuronal basis. In addition, also different networks were involved in the two processes compared with control conditions; bilateral striatum and the right lateral prefrontal cortex (lPFC) during helping and bilateral striatum as well as left lPFC and ventral medial prefrontal cortex (vmPFC) during punishment. Further we found that individual differences in empathic concern influenced whether people prefer to help or to punish. People with high empathic concern helped more frequently, were faster in their decision and showed higher activation in frontoparietal regions during helping compared with punishing. Our findings provide insights into the neuronal basis of human altruistic behavior and social norm enforcement mechanism.
Author Summary Temporal lobe epilepsy (TLE) is a disorder characterised by unpredictable seizures, where surgical removal of brain tissue is often the final treatment option. In roughly 30% of cases surgery procedures are unsuccessful at preventing future seizures. This paper shows the application of a computational model which uses patient derived brain connectivity to predict the success rates of surgery in people with TLE. We consider the brains of 22 patients as networks, with brain regions as nodes and the white matter connections between them as edges. The brain network is unique to each subject and produced from brain imaging scans of 22 patients and 39 controls. Seizures are simulated before and after surgery, where surgery in the model is the removal of nodes from the network. The model successfully identifies regions known to be involved in TLE, and its predicted success rates for surgery are close to the results found in reality. The model additionally provides patient specific recommendations for surgical procedures, which in simulations show improved results compared to standard surgery in every case. This is a first step towards designing personalised surgery procedures in order to improve surgery success rates.
Social rewards are important incentives for human behavior. This is especially true in team sports such as the most popular one worldwide: soccer. We investigated reward processing upon scoring a soccer goal in a standard two-versus-one situation and in comparison to winning in a monetary incentive task. The results show a strong overlap in brain activity between the two conditions in established reward regions of the mesolimbic dopaminergic system, including the ventral striatum and ventromedial pre-frontal cortex. The three main components of reward-associated learning i.e. reward probability (RP), reward reception (RR) and reward prediction errors (RPE) showed highly similar activation in both con-texts, with only the RR and RPE components displaying overlapping reward activity. Passing and shooting behavior did not correlate with individual egoism scores, but we observe a positive correlation be-tween egoism and activity in the left middle frontal gyrus upon scoring after a pass versus a direct shot. Our findings suggest that rewards in the context of soccer and monetary incentives are based on similar neural processes.
Refractory mesial temporal lobe epilepsy (mTLE) is a debilitating condition potentially amenable to resective surgery. However, between 40 and 50% patients continue to experience postoperative seizures. The development of imaging prognostic markers of postoperative seizure outcome is a crucial objective for epilepsy research. In the present study, we performed analyses of preoperative cortical thickness and subcortical surface shape on MRI in 115 of patients with mTLE and radiologically defined hippocampal sclerosis being considered for surgery, and 80 healthy controls. Patients with excellent (International League Against Epilepsy outcome (ILAE) I) and suboptimal (ILAE II-VI) postoperative outcomes had a comparable distribution of preoperative atrophy across the cortex, basal ganglia, and amygdala. Conventional volumetry of whole hippocampal and extrahippocampal subcortical structures, and of global gray and white matter, could not differentiate between patient outcome groups. However, surface shape analysis revealed localized atrophy of the thalamus bilaterally and of the posterior/lateral hippocampus contralateral to intended resection in patients with persistent postoperative seizures relative to those rendered seizure free. Data uncorrected for multiple comparisons also revealed focal atrophy of the ipsilateral hippocampus posterior to the margins of resection in patients with persistent seizures. This data indicates that persistent postoperative seizures after temporal lobe surgery are related to localized preoperative shape alterations of the thalamus bilaterally and the hippocampus contralateral to intended resection. Imaging techniques that have the potential to unlock prognostic markers of postoperative outcome in individual patients should focus assessment on a bihemispheric thalamohippocampal network in prospective patients with refractory mTLE being considered for temporal lobe surgery. Hum Brain Mapp 36:1637-1647, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
OBJECTIVE: There are competing explanations for persistent postoperative seizures after temporal lobe surgery. One is that 1 or more particular subtypes of mesial temporal lobe epilepsy (mTLE) exist that are particularly resistant to surgery. We sought to identify a common brain structural and connectivity alteration in patients with persistent postoperative seizures using preoperative quantitative magnetic resonance imaging and diffusion tensor imaging (DTI). METHODS: We performed a series of studies in 87 patients with mTLE (47 subsequently rendered seizure free, 40 who continued to experience postoperative seizures) and 80 healthy controls. We investigated the relationship between imaging variables and postoperative seizure outcome. All patients had unilateral temporal lobe seizure onset, had ipsilateral hippocampal sclerosis as the only brain lesion, and underwent amygdalohippocampectomy. RESULTS: Quantitative imaging factors found not to be significantly associated with persistent seizures were volumes of ipsilateral and contralateral mesial temporal lobe structures, generalized brain atrophy, and extent of resection. There were nonsignificant trends for larger amygdala and entorhinal resections to be associated with improved outcome. However, patients with persistent seizures had significant atrophy of bilateral dorsomedial and pulvinar thalamic regions, and significant alterations of DTI-derived thalamotemporal probabilistic paths bilaterally relative to those patients rendered seizure free and controls, even when corrected for extent of mesial temporal lobe resection. INTERPRETATION: Patients with bihemispheric alterations of thalamotemporal structural networks may represent a subtype of mTLE that is resistant to temporal lobe surgery. Increasingly sensitive multimodal imaging techniques should endeavor to transform these group-based findings to individualize prediction of patient outcomes. Ann Neurol 2015;77:760-774.
Emotions can be aroused by various kinds of stimulus modalities. Recent neuroimaging studies indicate that several brain regions represent emotions at an abstract level, i.e., independently from the sensory cues from which they are perceived (e.g., face, body, or voice stimuli). If emotions are indeed represented at such an abstract level, then these abstract representations should also be activated by the memory of an emotional event. We tested this hypothesis by asking human participants to learn associations between emotional stimuli (videos of faces or bodies) and non-emotional stimuli (fractals). After successful learning, fMRI signals were recorded during the presentations of emotional stimuli and emotion-associated fractals. We tested whether emotions could be decoded from fMRI signals evoked by the fractal stimuli using a classifier trained on the responses to the emotional stimuli (and vice versa). This was implemented as a whole-brain searchlight, multivoxel activation pattern analysis, which revealed successful emotion decoding in four brain regions: posterior cingulate cortex (PCC), precuneus, MPFC, and angular gyrus. The same analysis run only on responses to emotional stimuli revealed clusters in PCC, precuneus, and MPFC. Multidimensional scaling analysis of the activation patterns revealed clear clustering of responses by emotion across stimulus types. Our results suggest that PCC, precuneus, and MPFC contain representations of emotions that can be evoked by stimuli that carry emotional information themselves or by stimuli that evoke memories of emotional stimuli, while angular gyrus is more likely to take part in emotional memory retrieval.
Our decisions often have consequences for other people. Hence, self-interest and other-regarding motives are traded off in many daily-life situations. Interindividually, people differ in their tendency to behave prosocial. These differences are captured by the concept of social value orientation (SVO), which assumes stable, trait-like tendencies to act selfish or prosocial. This study investigates group differences in prosocial decision making and addresses the question of whether prosocial individuals act intuitively and selfish individuals instead need to control egoistic impulses to behave prosocially. We address this question via the interpretation of neuronal and behavioural indicators. In the present fMRI-study participants were grouped into prosocial- and selfish participants. They made decisions in multiple modified Dictator-Games (DG) that addressed self- and other-regarding motives to a varying extent (self gain, non-costly social gain, mutual gain, costly social gain). Selfish participants reacted faster than prosocial participants in all conditions, except for decisions in the non-costly social condition, in which selfish participants displayed the longest decision times. In the total sample we found enhanced neural activity in the ventromedial prefrontal cortex (vmPFC) and dorsomedial prefrontal cortex (dmPFC / BA 9) during decisions that resulted in non-costly social benefits. These areas have been implicated in cognitive control processes and deliberative value integration. Decisively, these effects were stronger in the group of selfish individuals. We believe that selfish individuals require more explicit and deliberative processing during prosocial decisions. Our results are compatible with the assumption that prosocial decisions in prosocials are more intuitive, whereas they demand more active reflection in selfish individuals.
Humans often evaluate their abilities by comparing their personal performance with that of others. For this process, it is critical whether the comparison turns out in one?s favor or against it. Here, we investigate how social comparisons of performance are encoded and integrated on the neural level. We collected functional magnetic resonance images while subjects answered questions in a knowledge quiz that was related to their profession. After each question, subjects received a feedback about their personal performance, followed by a feedback about the performance of a reference group who had been quizzed beforehand. Based on the subjects? personal performance, we divided trials in downward and upward comparisons. We found that upward comparisons correlated with activity in the dorsolateral prefrontal cortex and the anterior insula. Downward comparisons were associated with increased activation in the ventral striatum (VS), the medial orbitofrontal cortex and the ventral anterior cingulate cortex (ACC). The extent to which subjects outperformed the reference group modulated the activity in the VS and in the dorsal ACC. We suggest that the co-activation of the VS and the dorsal ACC contributes to the integration of downward comparisons into the evaluation of personal performance.
Current psychological concepts of social and ecological responsibility emphasize the relevance of altruism, suggesting that more altruistic individuals are more likely to engage in sustainable behaviors. Emerging evidence indicates a central role of the neuropeptide oxytocin in promoting altruism. Whether this influence extends to ecological responsibility or is limited to the social domain remains unknown. In two independent experiments involving 172 human participants, we addressed this question by exposing subjects to a sustainability-related monetary donation task, with the option to support either socially or ecologically framed charities. We found that oxytocin induced a context-dependent change in altruistic behavior away from pro-environmental toward pro-social donations, while keeping constant the overall proportion of donated money. This pro-social bias transcended to the domain of sustainable consumption. Collectively, our findings demonstrate that altruistic priorities vary as a function of oxytocin system activity, which has implications for the promotion of pro-environmental attitudes and eco-friendly behaviors. SIGNIFICANCE STATEMENT Individual responses to ecological and social sustainability require a shift in personal priorities away from selfish to more altruistic behaviors. Emerging evidence indicates a central role of the hypothalamic peptide oxytocin in promoting altruism, but whether the influence of oxytocin benefits altruistic decision-making in the context of ecological and social sustainability is unclear. In two independent behavioral experiments involving 172 human subjects, we show that heightened oxytocin system activity induces a social altruism bias at the cost of ecological responsibility. Our results have fundamental implications for policy interventions and business strategies designed to sustain ecological resources by suggesting that a social framing may attract more individuals to engage in pro-environmental and eco-friendly behaviors.
Vicarious embarrassment (VE) is an emotion triggered by the observation of others' pratfalls or social norm violations. Several explanatory approaches have been suggested to explain the source of this phenomenon, including perspective taking abilities or ingroup identification. Knowledge about its biological bases, however, is scarce. To gain a better understanding, the present study investigated neural activation patterns in response to video clips from reality TV shows. Reality TV is well known for presenting social norm violations, flaws and pratfalls of its protagonists in real life situations thereby qualifying as an ecological valid trigger for VE. \n\nMETHODS\nN=60 healthy participants viewed stand stills from previously watched video clips taken from German reality TV-shows while undergoing functional magnetic resonance imaging. The clips were preselected for high versus low VE content in a pilot study. Besides the investigation of differences in brain activation elicited by VE versus control stand stills (blocked design contrast), we performed additional exploratory functional connectivity analyses (psychophysiological interaction; PPI) to detect VE related brain networks. \n\nRESULTS\nCompared to the low VE condition, participants in the high VE condition showed a higher activation in the middle temporal gyrus, the supramarginal gyrus, the right inferior frontal gyrus and the gyrus rectus. Functional connectivity analyses confirmed increased connectivity of these regions with the anterior cingulate in the VE condition. Moreover, self-ratings of VE and brain activity were correlated positively. \n\nCONCLUSION\nReality TV formats with high VE content activate brain regions associated with Theory of Mind, but also with empathic concern and social identity. Therefore, our results support the idea that the ability to put oneself in other person's shoes is a major prerequisite for VE.
Social perception is an important prerequisite for successful social interaction, because it helps to gain information about behaviors, thoughts, and feelings of interaction partners. Previous pharmacological studies have emphasized the relevance of the oxytocin system for social perception abilities, while knowledge on genetic contributions is still scarce. In the endeavor to fill this gap in the literature, the current study searches for associations between participants’ social perception abilities as measured by the interpersonal perception task (IPT) and the rs2268498 polymorphism on the OXTR-gene, which has repeatedly been linked to processes relevant to social functioning. N = 105 healthy participants were experimentally tested with the IPT and genotyped for the rs2268498 polymorphism. T-allele carriers (TT and TC genotypes) exhibited significantly better performance in the IPT than carriers of the CC-genotype. This difference was also significant for the subscales measuring the strength of social functioning.
Research on empathy has a long tradition in clinical research, as deficits in empathy have been found in many mental disorders. Over decades, a large amount of measures for empathy have been developed, but in many cases these have not been analysed with respect to validity. Therefore, this paper aims to relate various assessment methods for empathy, schizotypy and autistic traits to gain knowledge on their convergent and discriminant validity. METHODS: A total of N = 108 participants were tested with two of the most widespread empathy questionnaires (Interpersonal Reactivity Index, Empathy Quotient), two behavioural paradigms (Reading the Mind in the Eyes Test, Cambridge Face-Voice Battery) and a rotation task. Furthermore, questionnaires assessing schizotypal and autistic traits were administered. RESULTS: Results indicate convergent validity of the applied empathy self-report measures, although their association with measures of schizotypal and autistic traits is inconsistent. However, results of the behavioural testing barely correlate either with the self-report measures or among each other. CONCLUSIONS: The questionnaire measures of empathy seem valid and exchangeable, and therefore suitable for capturing self-reported empathy in clinical research. The behavioural paradigms cover distinct endophenotypes of empathy and should only be used for very specific research questions.
Stress-related affective disorders have been identified as a core health problem of the twenty-first century. In the endeavor to identify vulnerability factors, personality has been discussed as a major factor explaining and predicting disorders like depression or burnout. An unsolved question is whether there are specific personality factors allowing differentiation of burnout from depression. The present study tested the relation between one of the most prominent, biological personality theories, Cloninger's Temperament and Character Inventory, and common measures of burnout (Maslach Burnout Inventory General) and depression (Beck Depression Inventory 2) in a sample of German employees (N = 944) and a sample of inpatients (N = 425). Although the same personality traits (harm avoidance and self-directedness) were predominantly associated with burnout and depression, there was a much stronger association to depression than to burnout in both samples. Besides, we observed specific associations between personality traits and subcomponents of burnout. Our results underline differences in the association of burnout vs. depression to personality, which may mirror differences in scope. While symptoms of depression affect all aspects of life, burnout is supposed to be specifically related to the workplace and its requirements. The much stronger association of personality to depression can be important to select appropriate therapy methods and to develop a more specified treatment for burnout in comparison to depression.
Patients with schizophrenia as well as individuals with high levels of schizotypy are known to have deficits in smooth pursuit eye movements (SPEM). Here, we investigated, for the first time, the neural mechanisms underlying SPEM performance in high schizotypy. Thirty-one healthy participants [N519 low schizotypes, N512 high schizotypes (HS)] underwent functional magnetic resonance imag- ing at 3T with concurrent oculographic recording while performing a SPEM task with sinusoidal stimuli at two velocities (0.2 and 0.4 Hz). Behaviorally, a significant interaction between schizotypy group and velocity was found for frequency of saccades during SPEM, indicating impairments in HS in the slow but not the fast condition. On the neural level, HS demonstrated lower brain activation in different regions of the occipital lobe known to be associated with early sensory and attentional processing and motion perception (V3A, middle occipital gyrus, and fusiform gyrus). This group difference in neural activation was independent of target velocity. Together, these findings replicate the observation of altered pursuit performance in highly schizotypal individuals and, for the first time, identify brain acti- vation patterns accompanying these performance changes. These posterior activation differences are compatible with evidence of motion processing deficits from the schizophrenia literature and, therefore, suggest overlap between schizotypy and schizophrenia both on cognitive-perceptual and neurophysio- logical levels. However, deficits in frontal motor areas observed during pursuit in schizophrenia were not seen here, suggesting the operation of additional genetic and/or illness-related influences in the clini- cal disorder.
Introduction: It has been hypothesized that two distinctive forms of Internet addiction exist. Here, generalized Internet addiction refers to the problematic use of the Internet covering a broad range of Internet-related activities. In contrast, specific forms of Internet addiction target the problematic use of distinct online activities such as excessive online video gaming or activities in social networks.
Methods: The present study investigates the relationship between generalized and specific Internet addiction in a cross-cultural study encompassing data from China, Taiwan, Sweden and Germany in n = 636 participants. In this study, we assessed - besides generalized Internet addiction - addictive behavior in the domains of online video gaming, online shopping, online social networks and online pornography.
Results: The results confirm the existence of distinct forms of specific Internet addiction. One exception, however, was established in five of the six samples under investigation: online social network addiction correlates in large amounts with generalized Internet addiction.
Discussion: In general, it is of importance to distinguish between generalized and specific Internet addiction.
Background: The prevalence of stuttering ismuch higher inmales compared to females. The biological underpin- nings of this skewed sex-ratio is poorly understood, but it has often been speculated that sex hormones could play an important role. Aims: The present study investigated a potential link between prenatal testosterone and stuttering. Here, an in- direct indicator ofprenatal testosterone levels, the Digit Ratio (2D:4D) ofthe hand, was used. As numerous stud- ies have shown, hands with more “male” characteristics (putatively representing greater prenatal testosterone levels) are characterized by a longer ring finger compared to the index finger (represented as a lower 2D:4D ratio) in the general population. Study design, subjects, outcome measures: We searched for differences in the 2D:4D ratios between 38 persons who stutter and 36 persons who do not stutter. In a second step, we investigated potential links between the 2D:4D ratio and the multifaceted symptomatology of stuttering, as measured by the Overall Assessment of the Speaker's Experience of Stuttering (OASES), in a larger sample of 44 adults who stutter. Results: In the first step, no significant differences in the 2D:4D were observed between individuals who stutter and individuals who do not stutter. In the second step, 2D:4D correlated negatively with higher scores of the OASES (representing higher negative experiences due to stuttering), and this effect was more pronounced for fe- male persons who stutter. Conclusions: The findings indicate for the first time that prenatal testosterone may influence individual differ- ences in psychosocial impact of this speech disorder.
Machiavellianism describes tendencies to behave amoral and distrusting with the aim of heightening one’s own status and maximizing personal benefit. In times of rising importance of ethic leadership and employee development, it is of large interest to better characterize the biological underpinnings of Machiavellian behavior endangering these rather new important aims for companies/organizations. The present study investigated in 630 healthy participants by means of a molecular genetic approach whether a prominent polymorphism of the DRD3 gene is associated with individual differences in Machiavellianism measured with the self-report scale Mach-IV. As the investigated DRD3 Ser9Gly (T/C) polymorphism (rs6280) has been associated with schizophrenia before, we also assessed schizotypy in a subgroup of participants as a personality trait measured by the SPQ-B. The present study yields evidence that schizotypal personality positively correlates with the construct of Machiavellianism. Moreover, the CC variant (Glycine/Glycine) is associated with highest Machiavellianism scores. These findings show that the neurotransmitter dopamine might play a crucial role in explaining the biological basis of Machiavellian behavior.
Support vector machine (SVM) Temporal lobe epilepsy (TLE) Brain network analysis White matter fiber tractography Diffusion tensor imaging (DTI) The objective of this study is to evaluate machine learning algorithms aimed at predicting surgical treatment out-comes in groups of patients with temporal lobe epilepsy (TLE) using only the structural brain connectome. Spe-cifically, the brain connectome is reconstructed using white matter fiber tracts from presurgical diffusion tensor imaging. To achieve our objective, a two-stage connectome-based prediction framework is developed that grad-ually selects a small number of abnormal network connections that contribute to the surgical treatment outcome, and in each stage a linear kernel operation is used to further improve the accuracy of the learned classifier. Using a 10-fold cross validation strategy, the first stage in the connectome-based framework is able to separate patients with TLE from normal controls with 80% accuracy, and second stage in the connectome-based framework is able to correctly predict the surgical treatment outcome of patients with TLE with 70% accuracy. Compared to existing state-of-the-art methods that use VBM data, the proposed two-stage connectome-based prediction framework is a suitable alternative with comparable prediction performance. Our results additionally show that machine learning algorithms that exclusively use structural connectome data can predict treatment outcomes in epilepsy with similar accuracy compared with " expert-based " clinical decision. In summary, using the unprecedented in-formation provided in the brain connectome, machine learning algorithms may uncover pathological changes in brain network organization and improve outcome forecasting in the context of epilepsy.
A wealth of research has explored whether marketing-based expectancies such as price and brand quality beliefs influence the consumption experience and subsequent behavior, but almost no research has examined individual differences in "marketing placebo effects." In this article, the authors suggest three moderators of the effect of marketing-based expectancies on the behavioral and neural measures of the consumption experience, based on previous findings from neuroscientific literature investigating traditional clinical pain placebo effects. They use a novel automated structural brain imaging approach to determine individual differences and combine this approach with traditional behavioral experiments. The findings show that consumers high in reward seeking, low in somatosensory awareness, and high in need for cognition are more responsive to marketing placebo effects.
OBJECTIVE Depression and burnout are two psychopathological labels that have been subject to an extensive discussion over the last decades. The crucial question is whether they can be seen as conceptually equal or as two distinct syndromes. One argument for the distinction is that depression impacts on the whole life of a suffering person whereas burnout is restricted to the job context. Depression has been shown to be affected by life stress. The more stressful life events a person experiences, the more he or she is susceptible for developing a depression. As there is the widespread but controversial opinion that burnout is a prodromal syndrome of depression, the present study examined whether the number of stressful life events is also associated with an increased risk for burnout. METHODS N=755 healthy participants and N=397 depressed patients completed the Maslach Burnout Inventory (MBI), the Beck Depression Inventory (BDI II) and reported the extent of experienced life stress. RESULTS A significantly closer relation between depression and life stress than between burnout and life stress was found in the healthy (z=3.01, p=.003) as well as in the depressed sample (z=3.41, p=.001). This finding was supported in both samples by means of a path analytic approach where the associations between life stress, burnout, and depression were controlled for possible mediator and moderator effects, also considering the influence of age. CONCLUSION By considering the influence of life stress it could be demonstrated that depression and burnout are not identical although they share substantial phenotypic variance (r=.46–.61). Most important, the trivariate associations are the same in a representative employee sample and in an inpatient clinical sample suggesting the same underlying mechanisms covering the whole range from normal behavior to psychopathology. However, only longitudinal data can show if burnout necessarily turns into depression with the consequence that the burnout – life stress association approaches the depression – life stress association over time.
Objective: This study aims to address possible associations between excessive use of the Internet and Attention Deficit/Hyperactivity Disorder (ADHD) and depression. As most of the studies on this topic were conducted in Asia, the aim of this investigation is to review the literature on this subject from Germany and examine problematic Internet use for potential associations with the propensity for depression and ADHD in a new, distinct German sample. Methods: A review of the literature was conducted. Subsequently, a total of N=895 healthy participants from Germany (413 males, 482 females) took part in a new study. Participants filled in questionnaires on their Internet usage, propensity for depression and ADHD. Results: The review of the literature revealed predominantly positive associations between problematic Internet use and depression, whereas only one study on the relationship between problematic Internet use and ADHD from Germany was found. The results from the current study showed that male participants had significantly higher scores on the Internet Addiction Test (IA-T) than female participants. Finally, the IA-T scores of the participants were linked to both the propensity for depression (r=.247, p<.01) and ADHD (r=.335, p<.01). This association was stronger for ADHD and in particular for the subscale “attention deficit”, as revealed by a post-hoc analysis. Conclusion: The results of this study are consistent with most of the research on this topic in other cultural circles and highlight the role of ADHD and depression when it comes to problematic Internet use. This study provides a basis for consideration about the clinical implications and treatment of comorbid problematic Internet use.
Jeffrey Gray's Reinforcement Sensitivity Theory (RST) represents one of the most influential biologically-based personality theories describing individual differences in approach and avoidance tendencies. The most prominent self-report inventory to measure individual differences in approach and avoidance behavior to date is the BIS/BAS scale by Carver and White (1994). As Gray and McNaughton (2000) revised the RST after its initial formulation in the 1970/80s, and given the Carver and White measure is based on the initial conceptualization of RST, there is a growing need for self-report inventories measuring individual differences in the revised behavioral inhibition system (BIS), behavioral activation system (BAS) and the fight, flight, freezing system (FFFS). Therefore, in this paper we present a new questionnaire measuring individual differences in the revised constructs of the BIS, BAS and FFFS in N = 1814 participants (German sample). An English translated version of the new measure is also presented and tested in N = 299 English language participants. A large number of German participants (N = 1090) also filled in the BIS/BAS scales by Carver and White (1994) and the correlations between these measures are presented. Finally, this same subgroup of participants provided buccal swaps for the investigation of the arginine vasopressin receptor 1a (AVPR1a) gene. Here, a functional genetic polymorphism (rs11174811) on the AVPR1a gene was shown to be associated with individual differences in both the revised BIS and classic BIS dimensions.
Acetylcholine (ACh) is a known modulator of several domains of cognition, among them attention, memory and learning. The neurotransmitter also influences the speed of information processing, particularly the detection of targets and the selection of suitable responses. We examined the effect of the rs1044396 (C/T) polymorphism of the gene encoding the nicotinic acetylcholine receptor α4-subunit (CHRNA4) on response speed and selective visual attention. To this end, we administered a Stroop task, a Negative priming task and an exogenous Posner-Cuing task to healthy participants (n = 157). We found that the CHRNA4 rs1044396 polymorphism modulated the average reaction times (RTs) across all three tasks. Dependent on the C allele dosage, the RTs linearly increased. Homozygous T allele carriers were always fastest, while homozygous C allele carriers were always slowest. We did not observe effects of this polymorphism on selective attention. In sum, we conclude that naturally occurring variations within the cholinergic system influence an important factor of information processing. This effect might possibly be produced by the neuromodulator system rather than the deterministic system of cortical ACh.
In many everyday decisions, people exhibit loss aversion—a greater sensitivity to losses relative to gains of equal size. Loss aversion is thought to be (at least partly) mediated by emotional—in particular, fear-related—processes. Decision research has shown that even incidental emotions, which are unrelated to the decision at hand, can influence decision making. The effect of incidental fear on loss aversion, however, is thus far unclear. In two studies, we experimentally investigated how incidental fear cues, presented during (Study 1) or before (Study 2) choices to accept or reject mixed gambles over real monetary stakes, influence monetary loss aversion. We find that the presentation of fearful faces, relative to the presentation of neutral faces, increased risk aversion—an effect that could be attributed to increased loss aversion. The size of this effect was moderated by psychopathic personality: Fearless dominance, in particular its interpersonal facet, but not self-centered impulsivity, attenuated the effect of incidental fear cues on loss aversion, consistent with reduced fear reactivity. Together, these results highlight the sensitivity of loss aversion to the affective context.
Most people are generous, but not toward everyone alike: generosity usually declines with social distance between individuals, a phenom- enon called social discounting. Despite the pervasiveness of social discounting, social distance between actors has been surprisingly neglected in economic theory and neuroscientific research. We used functional magnetic resonance imaging (fMRI) to study the neural basis of this process to understand the neural underpinnings of social decision making. Participants chose between selfish and generous alternatives, yielding either a large reward for the participant alone, or smaller rewards for the participant and another individual at a particular social distance. We found that generous choices engaged the temporoparietal junction (TPJ). In particular, the TPJ activity was scaled to the social-distance–dependent conflict between selfish and generous motives during prosocial choice, consistent with ideas that the TPJ promotes generosity by facilitating overcoming egoism bias. Based on functional coupling data, we propose and provide evidence for a biologically plausible neural model according to which the TPJ supports social discounting by modulating basic neural value signals in the ventromedial prefrontal cortex to incorporate social-distance– dependent other-regarding preferences into an otherwise exclusively own-reward value representation.
A dishonest person often utilizes another person's obliviousness to appropriate the property that belongs to the other person. Previous researchers have studied the making of a dishonest choice and the manipulation of truthful information. Here, we have investigated the neural correlates of processing the outcomes of dishonest decisions. Participants in this study were asked to interact with counterparts in an economic game. They could accept the counterparts' proposals on how to divide the profits (honest choice) or choose the alternative plan that was advantageous to themselves (dishonest choice), playing to the ignorance of their counterparts who had a 50% chance of detecting the situation. Successful dishonest choices (not being detected) would bring large rewards, whereas honest choices would lead to less of a reward, and failed dishonest choices (being caught) would result in no reward. Participants' neural responses during the outcome presentations were recorded by functional magnetic resonance imaging (fMRI) and event-related potential (ERP) methods in different sessions. We found that the outcomes of successful dishonest (vs. honest) choices elicited stronger activations in the ventral striatum and posterior cingulate cortex and a smaller ERP component called feedback-related negativity (FRN), which suggests that positive outcome evaluation and attention processing were aroused by successful dishonest choices. Moreover, the outcomes of failed dishonest (relative to honest) choices were associated with different neural response patterns in the medial orbitofrontal cortex and P3b ERP component between human and computer counterparts, suggesting that processing the output of social decision making (playing human) is different from that of risk taking (playing computer). The findings advanced our understanding about the neural processing of outcome presentation after a dishonest choice has been made.
Background Previous studies reported reduced volumes of many brain regions for temporal lobe epilepsy (TLE). It has also been suggested that there may be widespread changes in network features of TLE patients. It is not fully understood, however, how these two observations are related. Methods Using magnetic resonance imaging data, we perform parcellation of the brains of 22 patients with left TLE and 39 non-epileptic controls. In each parcellated region of interest (ROI) we computed the surface area and, using diffusion tensor imaging and deterministic tractography, infer the number of streamlines and their average length between each pair of connected ROIs. For comparison to previous studies, we use a connectivity 'weight' and investigate how ROI surface area, number of streamlines & mean streamline length contribute to such weight. Results We find that although there are widespread significant changes in surface area and position of ROIs in patients compared to controls, the changes in connectivity are much more subtle. Significant changes in connectivity weight can be accounted for by decreased surface area and increased streamline count. Conclusion Changes in the surface area of ROIs can be a reliable biomarker for TLE with a large influence on connectivity. However, changes in structural connectivity via white matter streamlines are more subtle with a relatively lower influence on connection weights.
Functional, molecular and genetic neuroimaging has highlighted the existence of brain anomalies and neural vulnerability factors related to obesity and eating disorders such as binge eating or anorexia nervosa. In particular, decreased basal metabolism in the prefrontal cortex and striatum as well as dopaminergic alterations have been described in obese subjects, in parallel with increased activation of reward brain areas in response to palatable food cues. Elevated reward region responsivity may trigger food craving and predict future weight gain. This opens the way to prevention studies using functional and molecular neuroimaging to perform early diagnostics and to phenotype subjects at risk by exploring different neurobehavioral dimensions of the food choices and motivation processes. In the first part of this review, advantages and limitations of neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), pharmacogenetic fMRI and functional near-infrared spectroscopy (fNIRS) will be discussed in the context of recent work dealing with eating behavior, with a particular focus on obesity. In the second part of the review, non-invasive strategies to modulate food-related brain processes and functions will be presented. At the leading edge of non-invasive brain-based technologies is real-time fMRI (rtfMRI) neurofeedback, which is a powerful tool to better understand the complexity of human brain-behavior relationships. rtfMRI, alone or when combined with other techniques and tools such as EEG and cognitive therapy, could be used to alter neural plasticity and learned behavior to optimize and/or restore healthy cognition and eating behavior. Other promising non-invasive neuromodulation approaches being explored are repetitive transcranial magnetic stimulation (rTMS) and transcranial direct-current stimulation (tDCS). Converging evidence points at the value of these non-invasive neuromodulation strategies to study basic mechanisms underlying eating behavior and to treat its disorders. Both of these approaches will be compared in light of recent work in this field, while addressing technical and practical questions. The third part of this review will be dedicated to invasive neuromodulation strategies, such as vagus nerve stimulation (VNS) and deep brain stimulation (DBS). In combination with neuroimaging approaches, these techniques are promising experimental tools to unravel the intricate relationships between homeostatic and hedonic brain circuits. Their potential as additional therapeutic tools to combat pharmacorefractory morbid obesity or acute eating disorders will be discussed, in terms of technical challenges, applicability and ethics. In a general discussion, we will put the brain at the core of fundamental research, prevention and therapy in the context of obesity and eating disorders. First, we will discuss the possibility to identify new biological markers of brain functions. Second, we will highlight the potential of neuroimaging and neuromodulation in individualized medicine. Third, we will introduce the ethical questions that are concomitant to the emergence of new neuromodulation therapies.
OBJECTIVE Limbic encephalitis (LE) is an autoimmune mediated disease leading to temporal lobe epilepsy, mnestic and psychiatric symptoms. In recent years, several LE subforms defined by serum antibody findings have been described. MRI usually shows volume changes of the amygdala and hippocampus. However, studies quantifying longitudinal volume changes in the acute disease stage are lacking. METHODS The aim of this retrospective observational study was to evaluate and quantify these volume changes by applying a fully automated volumetric approach to serial MRIs of 28 patients with antibody-associated LE. The results were compared with those of 28 age-matched and gender-matched healthy controls and analysed separately for the different antibody profiles and correlated with clinical parameters. Antibody profile analyses were exploratory due to the relatively small sample sizes. RESULTS We found distinct volumetric and clinical courses depending on the associated antibody. While LE associated with voltage-gated potassium channel-complex antibodies (VGKC-LE) showed highly significant larger volumes of both the amygdala and the hippocampus within the first 12 months after disease onset, LE associated with glutamic acid decarboxylase antibodies (GAD-LE) only displayed greater amygdala volumes at this disease stage. Both subgroups showed a reduction of the amygdala and hippocampus volumes during follow-up with higher volume changes in VGKC-LE. CONCLUSIONS These differences in the volumetric evolution corresponded to distinct clinical courses in terms of a more severe initial symptomatology regarding seizure, mnestic and psychiatric disturbances in VGKC-LE, which improved rapidly, corresponding to the evolution of the volumetric changes. In contrast to this, patients with GAD-LE were less severely affected at disease onset, showing a more unmodulated and chronic disease course during follow-up.
Some superior memorists demonstrated exceptional memory for reciting a large body of information. The underlying neural correlates, however, are seldom addressed. C.L., the current holder of Guinness World Record for reciting 67,890 digits in π, participated in this functional magnetic resonance imaging (fMRI) study. Thirteen participants without any mnemonics training were included as controls. Our previous studies suggested that C.L. used a digit-image mnemonic in studying and recalling lists of digits, namely associating 2-digit groups of "00" to "99" with images and generating vivid stories out of them (Hu et al., 2009). Thus, 2-digit condition was included, with 1-digit numbers and letters as control conditions. We hypothesized that 2-digit condition in C.L. should elicit the strongest activity in the brain regions which are associated with his mnemonic. Functional MRI results revealed that bilateral frontal poles (FPs, BA10), left superior parietal lobule (SPL), left premotor cortex (PMC), and left dorsolateral prefrontal cortex (DLPFC), were more engaged in both the study and recall phase of 2-digit condition for C.L. relative to controls. Moreover, the left middle/inferior frontal gyri (M/IFG) and intraparietal sulci (IPS) were less engaged in the study phase of 2-digit condition for C.L. (vs. controls). These results suggested that C.L. relied more on brain regions that are associated with episodic memory other than verbal rehearsal while he used his mnemonic strategies. This study supported theoretical accounts of restructured cognitive mechanisms for the acquisition of superior memory performance.
Neural representations of specific stimuli rely on activity pat- terns indistributedneuralassemblies [1–4]. According toone influential view, these assemblies are characterized by syn- chronized gamma-band activity (GBA) [5–11] that reflects stimulus-specific representations [12–14]. However, recent studies have shown that GBA is closely correlated with the overall amount of cellular activity and may be detrimental for precise representations of specific stimuli [15, 16]. Until now, the role of GBA for the formation of dynamically chang- ing representations has been unknown. Here, we applied representational similarity analysis (RSA) [17] to intracranial electroencephalogram (iEEG) data from ten presurgical epi- lepsy patients to identifystimulus-specificneural representa- tions. Patients first learned and then retrieved their paths throughvirtual houses. Dynamic representationswereidenti- fied by the rapidly changing distributions of frequency-spe- cific global (spatial) activity patterns across the brain. We found that GBA patterns during successful (but not unsuc- cessful) retrieval of one sequence were more similar to activ- ity during encodingof that same sequencecompared toother sequences. Thecontribution of individual electrodes to these global representations was correlated with local similarity in individual electrodes (i.e., with RSA across time). Moreover, time-resolved RSA values were negatively correlated with the magnitude of iEEG gamma power: RSA values were higher at time points when gamma power was reduced. Both global and local representations relied on a small pro- portion of electrodes. These results show that behaviorally relevant neural representations of specific dynamically changing stimuli can be tracked by iEEG recordings and that they are associated with reductions of gamma power.
2014
A central assumption in economics is that people misreport their private information if this is to their material benefit. Several recent models depart from this assumption and posit that some people do not lie or at least do not lie maximally. These models invoke many different underlying motives including intrinsic lying costs, altruism, efficiency concerns, or conditional cooperation. To provide an empirically-validated microfoundation for these models, it is crucial to understand the relevance of the different potential motives. We measure the extent of lying costs among a representative sample of the German population by calling them at home. In our setup, participants have a clear monetary incentive to misreport, misreporting cannot be detected, reputational concerns are negligible and altruism, efficiency concerns or conditional cooperation cannot play a role. Yet, we find that aggregate reporting behavior is close to the expected truthful distribution suggesting that lying costs are large and widespread. Further lab experiments show that this result is not driven by the mode of communication.
Decisions are said to be 'risky' when they are made in environments with uncertainty caused by nature. By contrast, a decision is said to be 'trusting' when its outcome depends on the uncertain decisions of another person. A rapidly expanding literature reveals economically important differences between risky and trusting decisions, and further suggests these differences are due to 'betrayal aversion'. While its neural foundations have not been previously illuminated, the prevailing hypothesis is that betrayal aversion stems from a desire to avoid negative emotions that arise from learning one's trust was betrayed. Here, we provide evidence from an fMRI study that supports this hypothesis. In particular, our data indicate that the anterior insula modulates trusting decisions that involve the possibility of betrayal.
Apart from everyday duties, such as doing the laundry or cleaning the house, there are tasks we do for pleasure and enjoyment. We do such tasks, like solving crossword puzzles or reading novels, without any external pressure or force; instead, we are intrinsically motivated: we do the tasks because we enjoy doing them. Previous studies suggest that external rewards, i.e., rewards from the outside, affect the intrinsic motivation to engage in a task: while performance-based monetary rewards are perceived as controlling and induce a business-contract framing, verbal rewards praising one’s competence can enhance the perceived self-determination. Accordingly, the former have been shown to decrease intrinsic motivation, whereas the latter have been shown to increase intrinsic motivation. The present study investigated the neural processes underlying the effects of monetary and verbal rewards on intrinsic motivation in a group of 64 subjects applying functional magnetic resonance imaging (fMRI). We found that, when participants received positive performance feedback, activation in the anterior striatum and midbrain was affected by the nature of the reward; compared to a non-rewarded control group, activation was higher while monetary rewards were administered. However, we did not find a decrease in activation after reward withdrawal. In contrast, we found an increase in activation for verbal rewards: after verbal rewards had been withdrawn, participants showed a higher activation in the aforementioned brain areas when they received success compared to failure feedback. We further found that, while participants worked on the task, activation in the lateral prefrontal cortex was enhanced after the verbal rewards were administered and withdrawn.
A rapid increase in the size of food portions has underlined the importance of understanding consumers' ability to accurately perceive portion sizes. Drawing on research on motivated perception, we posit that attitude ambivalence (simultaneously desiring a food and perceiving it as unhealthy) enhances visual sensitivity to increasing portion sizes. We manipulate or measure attitude ambivalence in three experimental studies conducted among children and adults and find that visual sensitivity is driven not simply by desire but by the coexistence of desire and perceived unhealthiness of the food (e.g., for hedonic food and among restrained eaters). Our findings suggest that framing foods as vices improves the estimation of portion sizes among health-conscious people.
Individuals with an autism spectrum disorder (ASD) show hallmark deficits in social perception. These difficulties might also reflect fundamental deficits in integrating visual signals. We contrasted predictions of a social perception and a spatial-temporal integration deficit account. Participants with ASD and matched controls performed two tasks: the first required spatiotemporal integration of global motion signals without social meaning, the second required processing of socially relevant local motion. The ASD group only showed differences to controls in social motion evaluation. In addition, gray matter volume in the temporal-parietal junction correlated positively with accuracy in social motion perception in the ASD group. Our findings suggest that social-perceptual difficulties in ASD cannot be reduced to deficits in spatial-temporal integration. © 2013 Springer Science+Business Media.
A great deal of perceptual and social information is conveyed by facial motion. Here, we investigated observers' sensitivity to the complex spatio-temporal information in facial expressions and what cues they use to judge the similarity of these movements. We motion-captured four facial expressions and decomposed them into time courses of semantically meaningful local facial actions (e.g., eyebrow raise). We then generated approximations of the time courses which differed in the amount of information about the natural facial motion they contained, and used these and the original time courses to animate an avatar head. Observers chose which of two animations based on approximations was more similar to the animation based on the original time course. We found that observers preferred animations containing more information about the natural facial motion dynamics. To explain observers' similarity judgments, we developed and used several measures of objective stimulus similarity. The time course of facial actions (e.g., onset and peak of eyebrow raise) explained observers' behavioral choices better than image-based measures (e.g., optic flow). Our results thus revealed observers' sensitivity to changes of natural facial dynamics. Importantly, our method allows a quantitative explanation of the perceived similarity of dynamic facial expressions, which suggests that sparse but meaningful spatio-temporal cues are used to process facial motion. © 2014 The Authors.
Esins Schultz, Wallraven and Bülthoff. Congenital prosopagnosia (CP), an innate impairment in recognizing faces, as well as the other-race effect (ORE), a disadvantage in recognizing faces of foreign races, both affect face recognition abilities. Are the same face processing mechanisms affected in both situations? To investigate this question, we tested three groups of 21 participants: German congenital prosopagnosics, South Korean participants and German controls on three different tasks involving faces and objects. First we tested all participants on the Cambridge Face Memory Test in which they had to recognize Caucasian target faces in a 3-alternative-forced-choice task. German controls performed better than Koreans who performed better than prosopagnosics. In the second experiment, participants rated the similarity of Caucasian faces that differed parametrically in either features or second-order relations (configuration). Prosopagnosics were less sensitive to configuration changes than both other groups. In addition, while all groups were more sensitive to changes in features than in configuration, this difference was smaller in Koreans. In the third experiment, participants had to learn exemplars of artificial objects, natural objects, and faces and recognize them among distractors of the same category. Here prosopagnosics performed worse than participants in the other two groups only when they were tested on face stimuli. In sum, Koreans and prosopagnosic participants differed from German controls in different ways in all tests. This suggests that German congenital prosopagnosics perceive Caucasian faces differently than do Korean participants. Importantly, our results suggest that different processing impairments underlie the ORE and CP.
Saccades to peripheral targets require a direct visuomotor transformation. In contrast, antisaccades, saccades in opposite direction of a peripheral target, require more complex transformation processes due to the inversion of the spatial vector. Here, the differential neural mechanisms underlying sensorimotor control in saccades and antisaccades were investigated using functional magnetic resonance imaging (fMRI) at 3 T field strength in 22 human volunteers. We combined a task factor (prosaccades: look towards target; antisaccades: look away from target) with a parametric factor of transformation demand (single vs. multiple peripheral targets) in a two-factorial block design. Behaviorally, a greater number of peripheral targets resulted in decreased spatial accuracy and increased reaction times in antisaccades. No effects were seen on the percentage of antisaccade direction errors or on any prosaccade measures. Neurally, a greater number of targets led to increased BOLD signal in the posterior parietal cortex (PPC) bilaterally. This effect was partially qualified by an interaction that extended into somatosensory cortex, indicating greater increases during antisaccades than prosaccades. The results implicate the PPC as a sensorimotor interface that is especially important in nonstandard mapping for antisaccades and point to a supportive role ofsomatosensory areas in antisaccade sensorimotor control, possibly by means of proprioceptive processes.
In daily life, responses are often facilitated by anticipatory imagery of expected targets which are announced by associated stimuli from different sensory modalities. Silent music reading represents an intriguing case of visuotonal modality transfer in working memory as it induces highly defined auditory imagery on the basis of presented visuospatial information (i.e. musical notes). Using functional MRI and a delayed sequence matching-to-sample paradigm, we compared brain activations during retention intervals (10 s) of visual (VV) or tonal (TT) unimodal maintenance versus visuospatial-to-tonal modality transfer (VT) tasks. Visual or tonal sequences were comprised of six elements, white squares or tones, which were low, middle, or high regarding vertical screen position or pitch, respectively (presentation duration: 1.5 s). For the cross-modal condition (VT, session 3), the visuospatial elements from condition VV (session 1) were re-defined as low, middle or high ‘‘notes’’ indicating low, middle or high tones from condition TT (session 2), respectively, and subjects had to match tonal sequences (probe) to previously presented note sequences. Tasks alternately had low or high cognitive load. To evaluate possible effects of music reading expertise, 15 singers and 15 non-musicians were included. Scanner task performance was excellent in both groups. Despite identity of applied visuospatial stimuli, visuotonal modality trans- fer versus visual maintenance (VT > VV) induced ‘‘inhibition’’ of visual brain areas and activation of pri- mary and higher auditory brain areas which exceeded auditory activation elicited by tonal stimulation (VT > TT). This transfer-related visual-to-auditory activation shift occurred in both groups but was more pronounced in experts. Frontoparietal areas were activated by higher cognitive load but not by modality transfer. The auditory brain showed a potential to anticipate expected auditory target stimuli on the basis of non-auditory information and sensory brain activation rather mirrored expectation than stimulation. Silent music reading probably relies on these basic neurocognitive mechanisms.
Decisions are said to be 'risky' when they are made in environments with uncertainty caused by nature. By contrast, a decision is said to be 'trusting' when its outcome depends on the uncertain decisions of another person. A rapidly expanding literature reveals economically important differences between risky and trusting decisions, and further suggests these differences are due to 'betrayal aversion'. While its neural foundations have not been previously illuminated, the prevailing hypothesis is that betrayal aversion stems from a desire to avoid negative emotions that arise from learning one's trust was betrayed. Here, we provide evidence from an fMRI study that supports this hypothesis. In particular, our data indicate that the anterior insula modulates trusting decisions that involve the possibility of betrayal.
It is ecologically adaptive that the amount of effort invested to achieve a reward increases the relevance of the resulting outcome. Here, we investigated the effect of effort on activity in reward and loss processing brain areas by using functional magnetic resonance imaging. In total, 28 subjects were endowed with monetary rewards of randomly varying magnitude after performing arithmetic calculations that were either difficult (high effort), easy (low effort) or already solved (no effort). Subsequently, a forced donation took place, where a varying part of the endowment was transferred to a charity organization, causing a loss for the subject. Results show that reward magnitude positively modulates activity in reward-processing brain areas (subgenual anterior cingulate cortex and nucleus accumbens) only in the high effort condition. Furthermore, anterior insular activity was positively modulated by loss magnitude only after high effort. The results strongly suggest an increasing relevance of outcomes with increasing previous effort.
Conflict monitoring is a process of stimulus evaluation and a pre-requisite for subsequent recruitment of cognitive control and behavioral adaptations. This study investigated how experimentally manipulated working-memory-related cognitive demand and aversive reinforcement modulate individual differences of conflict monitoring intensity and behavioral adjustments. Individual differences were assessed by means of an anxiety- related trait dimension (trait-BIS) and by means of reasoning abilities—a core determinant of intelligence. Moreover, we investigated the special role of verbal reasoning ability and figural reasoning ability for the modulation of the conflict monitoring intensity. Ninety participants performed a go/nogo task with four conditions each comprising a combination of low vs. high working-memory-related cognitive demand and low vs. high aversive reinforcement. No effect of aversive reinforcement was observed for the N2 amplitude. The fronto-central nogo N2 amplitude was more pronounced for high demand vs. low demand suggesting that cognitive demand served as an aversive costly event. Higher total reasoning abilities were associated with more intense conflict monitoring and shorter response times with increasing aversive reinforcement (defined as verbal error-feedback vs. monetary loss). Individuals with higher trait-BIS scores demonstrated a more intense conflict monitoring even in conditions with low aversive reinforcement and also a more cautious responding (i.e., response times slowing) with increasing aversive reinforcement indicating a focus on negative feedback prevention. The findings provide evidence for the conflict monitoring theory and suggest that working-memory-related demand overrules the impact of aversive reinforcement on conflict monitoring intensity. Reasoning abilities and anxiety-related traits go along with an intensification of conflict monitoring but differences in the flexibility of behavioral adjustment.
Approach to desirable events or stimuli of reward and avoidance of undesirable events or stimuli of non-reward or punishment are powerful forces to drive behavior. The importance of approach and avoidance motivation has been outlined in many psychological theories and traditions, including psychodynamics, behaviorism and cognitivism (Elliot and Covington, 2001). Of all theoretical accounts, the Reinforcement Sensitivity Theory (RST) by Jeffrey Gray is probably the most elaborate perspective on approach and avoidance (Gray, 1971; Gray and McNaughton, 2000). Key contributions by Gray within this framework are the identification of neural circuits underlying approach and avoidance behavior, the description of these circuits as neuropsychological systems with circumscribed functions in terms of a conceptual nervous system, and the development of a theory of personality based on individual differences in the reactivity of these systems.
An individual’s susceptibility to everyday cognitive failure constitutes a risk factor for physical and mental health. Different factors such as inefficiency of executive functioning and high trait impulsivity have been shown to affect this susceptibility. Furthermore, twin studies indicate a high heritability of failure suscep- tibility revealing genetic variables as an important biological influence. We tested for a molecular genetic association between variants on the dopamine D2 receptor gene (DRD2), which relate to executive con- trol and impulsivity, and susceptibility to everyday cognitive failure as assessed by the cognitive failure questionnaire (CFQ) in a sample of N = 500 (n = 140 male, n = 360 female, mean age M = 24.62, SD = 7.98) healthy participants of central European descent. Moreover, we assessed whether trait impulsivity as measured by the Barratt impulsiveness scale (BIS-11) qualifies as a mediator between DRD2 variants and CFQ scores. We found a positive association between DRD2 variants and the CFQ. This effect was in part yet not completely mediated by trait impulsivity. The DRD2 C/C variant constitutes a protective factor for the susceptibility to everyday cognitive failure. Results point towards at least two biopsychological pathways that may explain the observed effect.
In the recent past, various intrinsic connectivity networks (ICN) have been identified in the resting brain. It has been hypothesized that the fronto-parietal ICN is involved in attentional processes. Evidence for this claim stems from task-related activation studies that show a joint activation of the implicated brain regions during tasks that require sustained attention. In this study, we used functional magnetic resonance imaging (fMRI) to demonstrate that functional connectivity within the fronto-parietal network at rest directly relates to attention. We applied graph theory to functional connectivity data from multiple regions of interest and tested for associations with behavioral measures of attention as provided by the attentional network test (ANT), which we acquired in a separate session outside the MRI environment. We found robust statistical associations with centrality measures of global and local connectivity of nodes within the network with the alerting and executive control subfunctions of attention. The results provide further evidence for the functional significance of ICN and the hypothesized role of the fronto-parietal attention network.
The present review/perspectives article provides a short overview of our current understanding of the molecular genetics of personality. In the first part, the most important gene candidates such as COMT or SLC6A4 gene are presented. Since several seminal review studies have recently been published on dif- ferent facets of molecular genetics and personality/emotionality, we focus the second half of the present article on new relevant research directions. This includes a stronger focus on animal research based testing of candidate genes (e.g. neuropeptides such as oxytocin and vasopressin) and the use of á priori genotyp- ing to increase statistical power. Moreover, we stress the importance of integrating cross-cultural data in future research designs and of inclusion of epigenetic measures in neuroscientifically oriented person- ality research. Finally, the Affective Neuroscience Personality Scales are introduced as a new promising tool for biologically oriented psychology/psychiatry research.
In the present study we link self-report-data on personality to behavior recorded on the mobile phone. This new approach from Psychoinformatics collects data from humans in everyday life. It demonstrates the fruitful collaboration between psychology and computer science, combining Big Data with psychological variables. Given the large number of variables, which can be tracked on a smartphone, the present study focuses on the traditional features of mobile phones – namely incoming and outgoing calls and SMS. We observed N =49 participants with respect to the telephone/SMS usage via our custom developed mobile phone app for 5 weeks. Extraversion was positively associated with nearly all related telephone call variables. In particular, Extraverts directly reach out to their social network via voice calls.
The protein brain-derived neurotrophic factor (BDNF) plays an important role in diverse memory processes and is strongly expressed in the hippocampus. The hippocampus itself is a key structure involved in the processing of information from short-term to long-term memory. Due to the putative role of BDNF in memory consolidation, a prominent single nucleotide polymorphism (SNP) on the BDNF gene (BDNF Val66Met) was investigated in the context of long-term memory performance. N=138 students were presented with 40 words from 10 categories, each consisting of eight words such as 'fruits' or 'vehicles' in a memory recognition task (specifically the Deese-Roediger-McDermott Paradigm). Recognition performance was analyzed 25 min after the initial presentation of the word list and subsequently 1 week after the initial presentation. Overall, individual long-term memory performance immediately after learning the word list (T1) and performance 1 week later (T2) did not differ on the basis of the BDNF SNP, but an interaction effect of BDNF Val66Met by time-of-recall was found: Carriers of the Met66+ variant showed the strongest decline in hit rate performance over time.
BACKGROUND: A recent study yielded first evidence that personality plays an important role in explaining the influence of a prominent APOE polymorphism on cognitive decline and Alzheimer's disease (AD) in elderly humans. Adding to this, two earlier studies examined this polymorphism in the context of individual differences in temperament traits in young humans with mixed results. In general, research linking the prominent APOE ϵ2, ϵ3 and ϵ4 variants and human personality is of special interest, because an influence of this gene and its prominent polymorphism on personality in young adulthood could be of diagnostic value to predict AD and its development in later years.
RESULTS: In the present study N = 531 participants provided buccal swabs and filled in a self-report inventory measuring the Five Factor Model of Personality. No association between common genetic variations of the APOE gene (in detail the genotypes ϵ3/ϵ3, ϵ2/ϵ3 and ϵ3/ϵ4) and personality could be observed. The remaining genotypes, including the high risk constellation ϵ4/ϵ4 for AD, were too seldom to be tested.
CONCLUSIONS: In sum, the present study yielded no evidence for a direct link between common genetic variants of the APOE gene and personality in young adulthood.
Although the serotonin transporter length polymorphic region (5-HTTLPR) polymorphism is an extensively-investigated genetic marker of anxiety related personality traits (neuroticism and harm avoidance) and affective disorders, effect sizes in meta-analyses are small, if present at all, and all available primary studies to date lack mandatory statistical power. Moreover, questionnaire data is prone to confounding by variables such as social desirability. Therefore, extreme response style (ERS) is suggested as a new approach to elucidate the relationship between 5-HTTLPR and negative emotionality, as it is more implicit and of high reliability. N = 1075 healthy subjects were genotyped for 5-HTTLPR and a flanking polymorphism (rs25531) and filled out the NEO Five Factor Inventory and the Temperament Character Inventory. As dependent variable the number of extreme responses across all items was calculated. Using the common genotype or the triallelic approach (including rs25531) the meta-analytic findings could not be replicated. However, there was a significant association between 5-HTTLPR and extreme response style. Carriers of the L-allele or the L'-allele, respectively, had a significantly higher number of extreme responses than homozygous SS carriers across all items of the NEO Five Factor Inventory. This finding could be replicated in an alternative personality questionnaire (Affective Neuroscience Personality Scales, ANPS). There is a long tradition in psychological assessment indicating that ERS is an implicit measure of personality. Given the positive findings of the present study, ERS qualifies as a promising endophenotype in future genetic association studies on personality and affective disorders.
Previous work from Germany and Austria highlighted the importance of personality and excessive pri- vate Internet usage for Internet Addiction (IA). In a cross-cultural approach we tried to replicate a nega- tive association between IA and the personality trait of self-directedness in Bulgaria, Germany, Spain, Colombia, China, Taiwan and Sweden and as well the finding that persons with a damaged self-esteem have a higher proclivity for becoming Internet addicted in Bulgaria, Spain, Germany and Colombia. In total N = 989 took part in the study. Results show that the personality dimension self-directedness was negatively correlated to the IA score of the participants in all samples. In contrast, no interaction effect between implicit and explicit self-esteem on IA could be observed.
The main objective of this paper is to analyze the influence of mesial temporal lobe epilepsy (mTLE) on the morphology of the corpus callosum (CC) and its relation to cognitive abilities. More specifically, we investigated correlations between intellectual abilities and callosal morphology, while additionally exploring the modulating impact of (a) side of seizure onset (b) age of disease onset. For this reason a large representative sample of patients with hippocampal sclerosis (n=79; 35 males; 44 females; age: 18–63 years) with disease onset ranging from 0 to 50 years of age, and consisting of 46 left and 33 right mTLE-patients was recruited. Intelligence was measured using theWechsler-Adult Intelligence Scale Revised. To get localizations of correlations with high anatomic precision, callosal morphology was examined using computational mesh-based modeling methods, applied to anatomical brain MRI scans. Intellectual performance was positively associated with callosal thickness in anterior and midcallosal callosal regions, with anterior parts being slightly more affected by age of disease onset and side of seizure onset than posterior parts. Earlier age at onset of epilepsy was associated with lower thickness in anterior and midcallosal regions. In addi- tion, laterality of seizure onset had a significant influence on anterior CC morphology, with left hemispheric origin having stronger effects. We found that in mTLE, anterior and mid- callosal CC morphology are related to cognitive performance. The findings support recent findings of detrimental effects of early onset mTLE on anterior brain regions and of a dis- tinct effect particularly of left mTLE on frontal lobe functioning and structure. The causal nature of the relationship remains an open question, i.e., whether CC morphology impacts IQ development or whether IQ development impacts CC morphology, or both.
A particularly popular automated magnetic resonance imaging (MRI) hippocampal subfield mapping technique is the one described by Van Leemput et al. (2009: Hippocampus 19:549-557) that is currently distributed with FreeSurfer software. This method assesses the probabilistic locations of subfields based on a priori knowledge of subfield topology determined from high-field MRI. Many studies have applied this technique to conventionally acquired T1-weighted MRI data. In the present study, we investigated the relationship between this technique applied to conventional T1-weighted MRI data acquired at 3 T and postsurgical hippocampal histology in patients with medically intractable mesial temporal lobe epilepsy (mTLE) and hippocampal sclerosis (HS). Patients with mTLE (n = 82) exhibited significant volume loss of ipsilateral CA1, CA2-3, CA4-dentate gyrus (DG), subiculum, and fimbria relative to controls (n = 81). Histopathological analysis indicated that the most significant neuronal loss was observed in CA1, then CA4 and CA3, and more subtle neuronal loss in CA2, consistent with classical HS. Neuronal density of CA1 significantly correlated with MRI-determined volume of CA1, and increasingly so with CA2-3 and CA4-DG. Patients with increased HS based on histopathology had greater volume loss of the ipsilateral hippocampal regions on MRI. We conclude by suggesting that whilst time efficient and fully reproducible when applied to conventional single acquisition sequences, the use of the automated subfield technique described here may necessitate the application to multiacquisition high-resolution MR sequences for accurate delineation of hippocampal subfields.
We often make decisions with uncertain consequences. The outcomes of the choices we make are usually not perfectly predictable but probabilistic and the probabilities can be known or unknown. Probability judgments, i.e., the assessment of unknown probabilities can be influenced by evoked emotional states. This suggests that also the weighting of known probabilities in decision making under risk might be influenced by incidental emotions, i.e., emotions unrelated to the judgments and decisions at issue. Probability weighting describes the transformation of probabilities into subjective decision weights for outcomes and is one of the central components of cumulative prospect theory (CPT) that determine risk attitudes. We hypothesized that music-evoked emotions would modulate risk attitudes in the gain domain and in particular probability weighting. Our experiment featured a within-subject design consisting of four conditions in separate sessions. In each condition, the 41 participants listened to a different kind of music—happy, sad, or no music, or sequences of random tones—and performed a repeated pairwise lottery choice task. We found that participants chose the riskier lotteries significantly more often in the “happy” than in the “sad” and “random tones” conditions. Via structural regressions based on CPT, we found that the observed changes in participants’ choices can be attributed to changes in the elevation parameter of the probability weighting function: In the “happy” condition, participants showed significantly higher decision weights associated with the larger payoffs than in the “sad” and “random tones” conditions. Moreover, the elevation parameter correlated positively with self-reported music-evoked happiness. Thus, our experimental results provide evidence in favor of a causal effect of incidental happiness on risk attitudes that can be explained by changes in probability weighting.
Social norms, such as treating others fairly regardless of kin relations, are essential for the functioning of human societies. Their existence may explain why humans, among all species, show unique patterns of prosocial behaviour. The maintenance of social norms often depends on external enforcement, as in the absence of credible sanctioning mechanisms prosocial behaviour deteriorates quickly. This sanction-dependent prosocial behaviour suggests that humans strategically adapt their behaviour and act selfishly if possible but control selfish impulses if necessary. Recent studies point at the role of the dorsolateral prefrontal cortex (DLPFC) in controlling selfish impulses. We test whether the DLPFC is indeed involved in the control of selfish impulses as well as the strategic acquisition of this control mechanism. Using repetitive transcranial magnetic stimulation, we provide evidence for the causal role of the right DLPFC in strategic fairness. Because the DLPFC is phylogenetically one of the latest developed neocortical regions, this could explain why complex norm systems exist in humans but not in other social animals.
Interpersonal conflicts are a common element of many social relationships. One possible process in rebuilding social relationships is the act of apologizing. Behavioral studies have shown that apologies promote forgiveness. However, the neural bases of receiving an apology and forgiveness are still unknown. Hence, the aim of the present fMRI study was to investigate brain processes involved in receiving an apology and active forgiveness of an ambiguous offense. We asked one group of participants (player A) to make decisions, which were either positive or negative for another group of participants (player B). The intention of player A was ambiguous to player B. In case of a negative impact, participants in the role of player A could send an apology message to participants in the role of player B. Subsequently players B were asked whether they wanted to forgive player A for making a decision with negative consequences. We found that receiving an apology yielded activation in the left inferior frontal gyrus, the left middle temporal gyrus, and left angular gyrus. In line with previous research we found that forgiving judgments activated the right angular gyrus.
People often consider how their actions influence others when making decisions. However, we are not equally generous to everyone alike. Our willingness to share resources declines as a function of social distance between the decision maker and the recipient. This function is likely to be influenced by culture, but research on behavioral decision making is still lacking empirical evidence. In Western societies, individuals generally perceive themselves as autonomous and independent from others, whereas the distinction between self and close others is less sharply defined by Eastern individuals where relationships and group membership are more centralized. Therefore, the social discount function should reflect this difference in the distinction of self and others by a reduced decline in generosity over close social distances. A social decision-making task was adapted to the intercultural context, and data were collected in Germany and China. For seven different social distances, we estimated how much money German and Chinese subjects were willing to forego to give a certain reward to another person. A hyperbolic model was fitted to the data. We found that other-regarding generosity declines as a function of social distance independent of cultural identity. However, German subjects showed a marked drop in generosity across close social distances, which was significantly less pronounced in Chinese participants.
The new technological advances achieved during the last decade allowed the scientific community to investigate and employ neurophysiological measures not only for research purposes but also for the study of human behaviour in real and daily life situations. The aim of this review is to understand how and whether neuroscientific technologies can be effectively employed to better understand the human behaviour in real decision-making contexts. To do so, firstly, we will describe the historical development of neuromarketing and its main applications in assessing the sensory perceptions of some marketing and advertising stimuli. Then, we will describe the main neuroscientific tools available for such kind of investigations (e.g., measuring the cerebral electrical or hemodynamic activity, the eye movements, and the psychometric responses). Also, this review will present different brain measurement techniques, along with their pros and cons, and the main cerebral indexes linked to the specific mental states of interest (used in most of the neuromarketing research). Such indexes have been supported by adequate validations from the scientific community and are largely employed in neuromarketing research. This review will also discuss a series of papers that present different neuromarketing applications, such us in-store choices and retail, services, pricing, brand perception, web usability, neuropolitics, evaluation of the food and wine taste, and aesthetic perception of artworks. Furthermore, this work will face the ethical issues arisen on the use of these tools for the evaluation of the human behaviour during decision-making tasks. In conclusion, the main challenges that neuromarketing is going to face, as well as future directions and possible scenarios that could be derived by the use of neuroscience in the marketing field, will be identified and discussed.
2013
This study investigates how induced relative status affects satisfaction with different relative payoffs. We find that participants with lower status are more satisfied with disadvantageous payoff inequalities than equal or higher status participants. In contrast, when receiving an advantageous payoff, status does not affect satisfaction. Our findings suggest that relative social status has important implications for the acceptance of income inequalities.
This paper provides evidence that involuntary unemployment, and the segmentation of labor markets into firms offering “good” and “bad” jobs, may both arise as a consequence of contractual incompleteness. We provide a simple model that illustrates how unemployment and market segmentation may jointly emerge as part of a market equilibrium in environments where contracts are incomplete, in the sense that work effort is not third-party verifiable. Using experimental labor markets that differ only in the verifiability of work effort, we demonstrate empirically that contractual incompleteness can cause unemployment and segmentation. Our data are also consistent with the key channels through which the model explains the emergence of both phenomena. These include firms adopting a particular type of implicit contracting strategy, and feedback from market conditions to worker behavior.
Conformity is an important aspect of social behavior. Two main motives have been identified: people may adapt their behavior to "play nice" despite knowing better (normative conformity) or they may accept the others' opinion as a valid source of information (informative conformity). Neuroimaging studies can help to distinguish between these two possibilities. Here, we present a functional magnetic resonance imaging (fMRI) study on memory conformity in a real group situation. We investigated the effects of group pressure on activity in hippocampus and anterior cingulate cortex (ACC) which likely support informative and normative memory conformity, respectively. Furthermore, we related the single nucleotide polymorphism (SNP) rs4680 [called Catechol-O-methyltransferase (COMT) Val158Met] on the gene coding for COMT to both behavior and fMRI activation. Homozygous Met-allele carriers (Val-) behaved more conformist than carriers of at least one Val-allele (Val+). In the neuroimaging data, we compared trials in which subjects were confronted with a majority of incorrect group responses to trials in which they were confronted with a majority of correct group responses. We found increased hippocampal activity when the majority of the group was correct, possibly indicating retrieval processes. Moreover, we observed enhanced activity in the ACC when the majority of the group was incorrect, suggesting that conformity was mostly normative. Most interestingly, this latter effect was more pronounced for Val- as compared to Val+ participants. This offers a speculative explanation for the higher behavioral levels of social conformity in Val- allele carriers, because their subjectively perceived conflict in the presence of an incorrect group majority may have been higher. Overall, this study demonstrates how the mechanisms leading to complex social behavior such as conformity can be studied by combining genetic analyses and fMRI in social neuroscience paradigms.
Several studies reported changes in white matter architecture following temporal lobe surgery in patients with temporal lobe epilepsy (TLE) at short intervals after surgery. We investigated 20 patients with left-sided TLE using diffusion-imaging at two time points, that is, at 3-6 months and 12 months after surgery, to investigate postsurgical plasticity. We observed a loss of fiber tract integrity mainly in fiber tracts of the ipsilateral temporal lobe. Our data show that the remodeling of brain connectivity after surgical interventions continues for longer time periods. The functional implications of these plastic changes will have to be explored.
The possibility that market interaction may erode moral values is a long-standing, but controversial, hypothesis in the social sciences, ethics, and philosophy. To date, empirical evidence on decay of moral values through market interaction has been scarce. We present controlled experimental evidence on how market interaction changes how human subjects value harm and damage done to third parties. In the experiment, subjects decide between either saving the life of a mouse or receiving money. We compare individual decisions to those made in a bilateral and a multilateral market. In both markets, the willingness to kill the mouse is substantially higher than in individual decisions. Furthermore, in the multilateral market, prices for life deteriorate tremendously. In contrast, for morally neutral consumption choices, differences between institutions are small.
In their Research Article “Morals and markets” (10 May, p. 707), A. Falk and N. Szech gave participants a choice between saving the life of a mouse and receiving money. The value of the mouse's life was higher when participants sold it directly to the experimenter than when they bargained over the price with other participants.
This paper reports evidence from a city-wide field experiment on trust. About 1000 inhabitants of Zurich take part in a trust experiment, in which first movers can condition their investments on the residential districts of second movers. First movers differentiate their investments systematically depending on where in Zurich the second mover lives. The observed discrimination pattern is robust as indicated by additional data collected in a newspaper study and a laboratory experiment. Economic status seems to be key for a district's reputation: first movers invest more if second movers live in high-income districts. Investments into districts are positively correlated with the corresponding willingness to repay, which indicates that first movers correctly anticipate the relative trustworthiness of inhabitants of different districts. Furthermore, we find that people trust strangers from their own district significantly more than strangers from other districts. This in-group effect is, at least partly, driven by more accurate beliefs about the trustworthiness of in-group members.
This article studies how a taste for consistency affects decision making. Our application is response behavior in surveys. In particular, we show that the inclusion of questions can affect answers to subsequent related questions. The reason is that participants want to respond in a consistent way. Studying three different surveys, we find a systematic effect of the inclusion of additional questions. The effects are large and reveal how easy survey responses can be manipulated. For example, we find that a subtle manipulation reduced the number of people who agreed that a murderer should be imprisoned for the rest of his life by more than 20 percentage points.
Field evidence suggests that people belonging to the same group often behave similarly, that is, behavior exhibits social interaction effects. We conduct a laboratory experiment that avoids the identification problem present in the field and allows us to study the behavioral logic of social interaction effects. Our novel design feature is that each subject is simultaneously a member of two randomly assigned and identical groups where only members (“neighbors”) are different. We study behavior in a coordination game with multiple equilibria and a public goods game, which has only one equilibrium in material payoffs. We speak of social interactions if the same subject at the same time makes group-specific decisions that depend on their respective neighbors’ decisions. We find that a majority of subjects exhibit social interaction effects both when the game has multiple equilibria in material payoffs and when it only has one equilibrium.
Social preference research has received considerable attention among economists in recent years. However, the empirical foundation of social preferences is largely based on laboratory experiments with self-selected students as participants. This is potentially problematic as students participating in experiments may behave systematically different than nonparticipating students or nonstudents. In this paper we empirically investigate whether laboratory experiments with student samples misrepresent the importance of social preferences. Our first study shows that students who exhibit stronger prosocial inclinations in an unrelated field donation are not more likely to participate in experiments. This suggests that self-selection of more prosocial students into experiments is not a major issue. Our second study compares the behavior of students and participants recruited from the general population in a trust experiment. In general, we find very similar behavioral patterns for the two groups, but nonstudents make significantly more generous repayments suggesting that results from student samples might be seen as a lower bound for the importance of prosocial behavior.
Mesial temporal lobe epilepsy is the most common type of focal epilepsy and in its course often becomes refractory to anticonvulsant pharmacotherapy. A resection of the mesial temporal lobe structures is a promising option in these cases. However, approximately 30% of all patients remain with persistent seizures after surgery. In other words, reliable criteria for patients' outcome prediction are absent. To address this limitation, we investigated pre-surgical brain morphology of patients with unilateral left mesial temporal lobe epilepsy who underwent a selective amygdalohippocampectomy. Using support vector classification, we aimed to predict the post-surgical seizure outcome of each patient based on the pre-surgical T1-weighted structural brain images. Due to morphological gender differences and the evidence that men and women differ in onset, prevalence and symptomology in most neurological diseases, we investigated male and female patients separately. Thus, we benefitted from the capability to validate the reliability of our method in two independent samples. Notably, we were able to accurately predict the individual patients' outcome in the male (94% balanced accuracy) as well as in the female (96% balanced accuracy) group. In the male cohort relatively larger white matter volumes in the favorable as compared to the non-favorable outcome group were identified bilaterally in the cingulum bundle, fronto-occipital fasciculus and both caudate nuclei, whereas the left inferior longitudinal fasciculus showed relatively larger white matter volume in the non-favorable group. While relatively larger white matter volumes in the female cohort in the left inferior and right middle longitudinal fasciculus were associated with the favorable outcome, relatively larger white matter volumes in the non-favorable outcome group were identified bilaterally in the superior longitudinal fasciculi I and II. Here, we observed a clear lateralization and distinction of structures involved in the classification in men as compared to women with men exhibiting more alterations in the hemisphere contralateral to the seizure focus. In conclusion, individual post-surgical outcome predictions based on a single T1-weighted magnetic resonance image seem plausible and may thus support the routine pre-surgical workup of epilepsy patients.
The Attentional Blink phenomenon (AB) describes a transient deficit in temporally selective visual attention regarding the processing of the second of two target stimuli in a rapid serial visual presentation (RSVP) task. The AB is a very prominent paradigm in the Cognitive Neurosciences that has been extensively studied by diverse psychophysiological techniques such as EEG or fMRI. Association studies from molecular genetics are scarce although the high heritability of higher cognitive functioning is proven. Only one seminal study reported an association between AB magnitude and the dopamine receptor D2 (DRD2) C957T polymorphism (Colzato et al., 2011). This functional polymorphism influences striatal D2 receptor binding affinity and thereby the efficacy of dopaminergic neurotransmission which is important for working memory and attentional processes. Colzato et al. (2011) reported that DRD2 C957T T/T-carriers exhibit a significant smaller AB than C-allele carriers. In the present study this influence of the DRD2 SNP on the AB could not be replicated in N=211 healthy participants. However, a significantly larger lag 1 sparing was observed for homozygous T/T-carriers. Moreover, carriers of at least one T-allele showed a significantly poorer performance in the identification of T1. In general, these results support the notion of a role of the dopaminergic system on the AB. However, as our results do not parallel previous findings the exact nature of this influence and its dependence on task parameters will have to be examined in further genetic association studies.
It is ecologically adaptive that the amount of effort invested to achieve a reward increases the relevance of the resulting outcome. Here, we investigated the effect of effort on activity in reward and loss processing brain areas by using functional magnetic resonance imaging. In total, 28 subjects were endowed with monetary rewards of randomly varying magnitude after performing arithmetic calculations that were either difficult (high effort), easy (low effort) or already solved (no effort). Subsequently, a forced donation took place, where a varying part of the endowment was transferred to a charity organization, causing a loss for the subject. Results show that reward magnitude positively modulates activity in reward-processing brain areas (subgenual anterior cingulate cortex and nucleus accumbens) only in the high effort condition. Furthermore, anterior insular activity was positively modulated by loss magnitude only after high effort. The results strongly suggest an increasing relevance of outcomes with increasing previous effort.
Purpose Chronic low back pain (CLBP) is one of the most important pain disorders with increasing social and economic implications. Given that CLBP is a multidi- mensional process associated with comorbidities such as anxiety and depression, treatment of chronic low back pain is still a challenge. Advancement of in vivo brain imaging technologies has revealed increasing insights into the etiology and pathogenesis ofchronic pain; however, the exact mechanisms of chronification of LBP remain still unclear. The purpose of the present study was to analyse the neu- rostructural alterations in CLBP and to evaluate the role of comorbidities and their neurostructural underpinnings.
PURPOSE: To determine regional alterations of fractional anisotropy (FA) and mean diffusivity (MD) in patients with magnetic resonance imaging (MRI)-negative temporal lobe epilepsy with unknown cause (TLEu) using diffusion tensor imaging (DTI) and voxel-based statistics (VBS). METHODS: Ten patients with left TLEu and no abnormality on conventional MRI and 81 age-matched neurological healthy controls were studied. VBS analyses were used to compare FA and MD differences between patients and controls. All results were reported using stringent statistical thresholds corrected for multiple comparisons. RESULTS: Patients with TLEu had widespread and bilateral reduction of white matter FA, encompassing the temporal lobes, entire corpus callosum, thalamus, and other regions relative to controls. Increased MD was more spatially limited in patients, but was also observed in the thalamus. FA of the putamen was significantly increased bilaterally in patients relative to controls, which correlated with increasing macroscopic atrophy of the putamen. DISCUSSION: Water diffusion abnormalities are widespread and bilaterally distributed in patients with unilateral TLEu, which are beyond the resolution of conventional MRI. FA alterations are more widespread relative to MD alterations. This is the first study to show evidence of interrelated microscopic (ie, FA increase) and macroscopic (ie, atrophy) alterations of the putamen in patients with TLEu.
The oxytocin and the dopaminergic systems have turned out to be highly relevant for social abilities and cognition. Therefore, we examined the association between two functional gene polymorphisms and face cognition (FC) in a multivariate study (N = 250) by applying structural equation modeling. The catechol-O-methyltransferase (COMT) val158met polymorphism influences the enzyme activity of COMT, which affects the prefrontal dopamine concentration. The rs226849 is a single-nucleotide polymorphism located in the promoter region of the oxytocin receptor (OXTR) gene, modulating the mRNA expression. By modeling a general fluid ability factor (defined by working memory and reasoning) and nested FC factors, we tested genetic contributions to FC, after controlling for variance in FC that was also associated with fluid abilities. In line with several previous studies, we found a significant association between the COMT genotype and fluid abilities (Gf) but not with FC. The association between the oxytocin polymorphism and Gf was opposite in direction for men and women. Women with the C(+) genotype performed better on Gf tasks than those with the C(-) genotype. Conversely, men with the C(-) genotype performed better than those with the C(+) genotype. There was no significant association between OXTR and the nested FC factor. Therefore, the relationship between the oxytocin polymorphism and FC can be fully accounted for by Gf. The sex specificity of this relationship is a novel finding and warrants a mechanistic explanation.
The motives underlying prosocial behavior, like charitable donations, can be related either to actions or to outcomes. To address the neural basis of outcome orientation in charitable giving, we asked 33 subjects to make choices affecting their own payoffs and payoffs to a charity organization, while being scanned by functional magnetic resonance imaging (fMRI). We experimentally induced a reward prediction error (RPE) by subsequently discarding some of the chosen outcomes. Co-localized to a nucleus accumbens BOLD signal corresponding to the RPE for the subject's own payoff, we observed an equivalent RPE signal for the charity's payoff in those subjects who were willing to donate. This unique demonstration of a neuronal RPE signal for outcomes exclusively affecting unrelated others indicates common brain processes during outcome evaluation for selfish, individual and nonselfish, social rewards and strongly suggests the effectiveness of outcome-oriented motives in charitable giving.
Humans often evaluate their abilities by comparing their personal performance with that of others. For this process, it is critical whether the comparison turns out in one's favor or against it. Here, we investigate how social comparisons of performance are encoded and integrated on the neural level. We collected functional magnetic resonance images while subjects answered questions in a knowledge quiz that was related to their profession. After each question, subjects received a feedback about their personal performance, followed by a feedback about the performance of a reference group who had been quizzed beforehand. Based on the subjects' personal performance, we divided trials in downward and upward comparisons. We found that upward comparisons correlated with activity in the dorsolateral prefrontal cortex and the anterior insula. Downward comparisons were associated with increased activation in the ventral striatum (VS), the medial orbitofrontal cortex and the ventral anterior cingulate cortex (ACC). The extent to which subjects outperformed the reference group modulated the activity in the VS and in the dorsal ACC. We suggest that the co-activation of the VS and the dorsal ACC contributes to the integration of downward comparisons into the evaluation of personal performance.
The present study focuses on the neurostructural foundations of the human personality. In a large sample of 227 healthy human individuals (168 women and 59 men), we used MRI to examine the relationship between personality traits and both regional gray and white matter volume, while controlling for age and sex. Personality was assessed using the German version of the NEO Five-Factor Inventory that measures individual differences in the 'Big Five of Personality': extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience. In contrast to most previous studies on neural correlates of the Big Five, we used improved processing strategies: white and gray matter were independently assessed by segmentation steps before data analysis. In addition, customized sex-specific diffeomorphic anatomical registration using exponentiated lie algebra templates were used. Our results did not show significant correlations between any dimension of the Big Five and regional gray matter volume. However, among others, higher conscientiousness scores correlated significantly with reductions in regional white matter volume in different brain areas, including the right insula, putamen, caudate, and left fusiformis. These correlations were driven by the female subsample. The present study suggests that many results from the literature on the neurostructural basis of personality should be reviewed carefully, considering the results when the sample size is larger, imaging methods are rigorously applied, and sex-related and age-related effects are controlled.
Dopaminergic activity is modulated by acetylcholine with relevance for cognitive functioning, as shown by pharmacological work in a rodent model. In humans, the two transmitter systems' joint effort on cognition has been described on the molecular genetic level: DRD2 rs6277, a single nucleotide polymorphism (SNP) on the dopamine D2 receptor gene and CHRNA4 rs1044396, a SNP on the nicotinic acetylcholine receptor gene interact on visuo-spatial and phonological working memory. The present study uses structural MRI and voxel based morphometry to extend this behavioral work to an intermediate phenotype on the neural level. We found significantly reduced gray matter volume in the right putamen in carriers of the DRD2 C/C and CHRNA4 T/T groups. This genotype combination has previously proven to be beneficial for working memory capacity. Results are in line with the idea that the two genes jointly influence the gating signals from subcortical structures to the prefrontal cortex.
In the recent past, various intrinsic connectivity networks (ICN) have been identified in the resting brain. It has been hypothesized that the fronto-parietal ICN is involved in attentional processes. Evidence for this claim stems from task-related activation studies that show a joint activation of the implicated brain regions during tasks that require sustained attention. In this study, we used functional magnetic resonance imaging (fMRI) to demonstrate that functional connectivity within the fronto-parietal network at rest directly relates to attention. We applied graph theory to functional connectivity data from multiple regions of interest and tested for associations with behavioral measures of attention as provided by the attentional network test (ANT), which we acquired in a separate session outside the MRI environment. We found robust statistical associations with centrality measures of global and local connectivity of nodes within the network with the alerting and executive control subfunctions of attention. The results provide further evidence for the functional significance of ICN and the hypothesized role of the fronto-parietal attention network.
Recent functional imaging studies that examined functional connectivity in the resting brain have demonstrated various intrinsic connectivity networks (ICNs). Certain patterns of over- and underactivity in various ICNs have been hypothesized to form the neural basis of psychiatric disorders. Furthermore, activity in the ICNs does not reflect ongoing mental activity but the maintenance of neural circuits in a ready state suggesting not only relationships between ICNs and disorders but also correlations between ICNs and personality. In the present study, we assess the relationship between trait anxiety, a well established endophenotype of anxiety disorders, and functional connectivities within the insular salience ICN in a sample of healthy female subjects. Based on a previous study that demonstrated the functional relevance of the insular salience ICN for state anxiety, we used the harm avoidance scale from the Temperament and Character Inventory (TCI) as a trait marker to demonstrate increased functional connectivity within the insular salience ICN. Specifically, the functional connectivity between the anterior insula and the anterior cingulate and between the anterior insula and the dorsolateral prefrontal cortex were positively correlated with individual harm avoidance scores. The results fit into previous work, provide evidence for a potential biomarker of anxiety disorders and, most importantly, demonstrate a direct neural correlate of the personality trait harm avoidance in the absence of external stimulation.
The investigation of the interaction of genes and environment in the context of mental health and personality yields important new insights for a better understanding of human nature. Both antenatal and postnatal environmental factors have been considered as potential modulators of genetic activity. Antenatally, especially smoking or alcohol drinking habits of the mother dramatically influence the health of the child during pregnancy and even later on in life. In the present study we would like to introduce a more "distant" factor that is not under the control of the becoming mother but that nevertheless plays a potential role for the health of the unborn child later on in adulthood. Here, we retrospectively investigate the influence of solar activity (while the child is still in the uterus of the becoming mother) on brain structure (with a focus on hippocampus and amygdala volume) and personality in adulthood. We observe an interaction of a genetic variant (rs41423247) of the glucocorticoid receptor gene (NR3C1) and solar activity in the first trimester after conception on both hippocampal volume and the personality trait neuroticism in adulthood in N = 254 participants. The NR3C1 gene is the focus of interest, because of its influence on the hypothalamic-pituitary-adrenal (HPA) axis and negative emotionality. Carriers of the CC variant of rs41423247 grown in the womb under the influence of high sun radiation (high solar activity) show both the highest hippocampal volume in the left hemisphere and lowest neuroticism scores. The present findings should encourage researchers in psychology and psychiatry to include also environmental influences such as solar activity besides genetics to better understand the etiogenesis of psychiatric disorders.
This review provides a short overview of the most significant biologically oriented theories of human personality. Personality concepts of Eysenck, Gray and McNaughton, Cloninger and Panksepp will be introduced and the focal evidence for the heritability of personality will be summarized. In this context, a synopsis of a large number of COMT genetic association studies (with a focus on the COMT Val158Met polymorphism) in the framework of the introduced biologically oriented personality theories will be given. In line with the theory of a continuum model between healthy anxious behavior and related psychopathological behavior, the role of the COMT gene in anxiety disorders will be discussed. A final outlook considers new research strategies such as genetic imaging and epigenetics for a better understanding of human personality.
The emotion of anxiety represents one of the most studied topics in the neurosciences, in part due to its relevance for understanding the evolution- ary development of the human brain and its role in the pathogenesis of psychopathological conditions. Struc- tural magnetic resonance imaging (sMRI) has enabled mapping of the anxious human brain and has contrib- uted substantially to the understanding of anxiety. Alongside the fields of clinical psychology/psychiatry, personality psychology aims to support the research endeavor of mapping the anxious brain and has found that individual differences in anxiety-related personal- ity dimensions such as Neuroticism or Harm Avoidance (measured by self-report) are correlated with gray and white matter volumes in different areas of the human brain. This review reveals that structures including parts of the frontal cortex (e.g., the orbitofrontal cor- tex) and the temporal lobe (e.g., the hippocampus) are often associated with trait anxiety, and it points out the inconsistencies that exist in the personality-sMRI litera- ture on human anxiety. Consequently, we suggest new research strategies to overcome the inconsistencies. This review outlines how results from animal research can guide scientists in developing testable hypotheses in search of the anxious brain. Moreover, genetic imag- ing is presented as an interesting approach to mapping the anxious brain.
The present study investigates the link between volumetric hemispheric ratios (VHRs) and personality measures in N=267 healthy participants using Eysenck's Personality Inventory-Revised (EPQ-R) and the BIS/BAS scales. A robust association between extraversion and VHRs was observed for gray matter in males but not females. Higher gray matter volume in the left than in the right hemisphere was associated with higher extraversion in males. The results are discussed in the context of positive emotionality and laterality of the human brain.
This review provides a short overview of the most significant biologically oriented theories of human personality. Personality concepts of Eysenck, Gray and McNaughton, Cloninger and Panksepp will be introduced and the focal evidence for the heritability of personality will be summarized. In this context, a synopsis of a large number of COMT genetic association studies (with a focus on the COMT Val158Met polymorphism) in the framework of the introduced biologically oriented personality theories will be given. In line with the theory of a continuum model between healthy anxious behavior and related psychopathological behavior, the role of the COMT gene in anxiety disorders will be discussed. A final outlook considers new research strategies such as genetic imaging and epigenetics for a better understanding of human personality.
Intertemporal choices between a smaller sooner and a larger delayed reward are one of the most important types of decisions humans face in their everyday life. The degree to which individuals discount delayed rewards correlates with impulsiveness. Steep delay discounting has been associated with negative outcomes over a wide range of behaviors such as addiction. However, little is known about the biological foundations of delay discounting. Here, we examine a potential causal link between delay discounting and testosterone, a hormone which has been associated with other types of impulsive behavior. In our double-blind placebo-controlled study 91 healthy young men either received a topical gel containing 50mg of testosterone (N=46) or a placebo (N=45) before participating in a delay discounting task with real incentives. Our main finding is that a single dose administration of testosterone did not lead to significant differences in discount rates between the placebo and the testosterone group. Within groups and in the pooled sample, no significant relationship between testosterone and discount rates was observed. At the same time, we do replicate standard findings from the delay discounting literature such as a magnitude-of-rewards effect on discount rates. In sum, our findings suggest that circulating testosterone does not have a significant effect on delay discounting in young men.
One of the most prominent paradigms in neuroeconomics is the ultimatum game (UG) that provides a framework for the study of pro-social behavior in two players interacting anonymously with each other: Player 1 has to split an endowment with player 2. Player 2 can either accept or reject the offer from player 1. If player 2 accepts the offer then the money is split as proposed by player 1. In case of rejection both players get nothing. Until now only one twin study investigated the heritability of the behavior in the UG. Results indicated a strong heritability for the decision behavior of player 2 whereas no genetic influence on player 1 behavior could be detected. Further studies are mandatory to validate these heritability estimates. However, a first candidate polymorphism, the DRD4 exon III, constituting the biological basis of the heritability in the responder behavior has already been identified in a Chinese sample (Zhong et al., 2010). Until now genetic studies in Caucasians on the UG are lacking. The present study wants to fill this gap by investigating the UG in a healthy German sample. Moreover, we intend to find candidate genes that are associated with the first-mover-behavior. In a sample of N = 130 healthy participants an online version of the UG was conducted and polymorphisms of the dopamine D2 receptor gene (DRD2) and the DRD4 exon III VNTR were genotyped. We could confirm the DRD4 exon III effect on the responder behavior and the absence of an effect on the proposer behavior reported before. In line with Zhong et al. (2010) carriers of the 4/4 genotype showed a significant higher minimal acceptable offer (p = 0.023) than subjects with any other genotype. Furthermore, a DRD2-haplotype-block containing the single nucleotide polymorphisms rs1800497 and rs2283265 was significantly associated with the amount player1 offered (p = 0.005) but not with the decision of player 2. Results support the importance of the dopaminergic system for pro-social behavior.
Are people more likely to infringe on a legal obligation if they perceive it as unfair? This question is especially relevant in situations with low potential punishment for disobeying an obligation, i.e., with expressive law. To explore this issue, we present experimental evidence on how expressive law affects behavior if the law defines asymmetric obligations for ex ante identical individuals. To implement expressive law we introduce very weakly incentivized obligations, i.e., minimum contribution levels, in a repeated public goods experiment. Our main finding is that, in an environment with asymmetric obligations, people adhere to their individual obligation to the same extent as in an environment with symmetric obligations. This result is compatible with the argument that expressive law affects behavior by attaching an emotional cost of disobeying the own obligation such as a loss in self-esteem. We only find a significant temporary effect of obligations that vanishes in the long run.
https://doi.org/10.1016/j.joep.2012.12.003
Although oxytocin (OT) has become a major target for the investigation of positive social processes, it can be assumed that it exerts its effects in concert with other neurotransmitters. One candidate for such an interaction is dopamine (DA). For both systems, genetic variants have been identified that influence the availability of the particular substance. A variant of the gene coding for the transmembrane protein CD38 (rs3796863), which is engaged in OT secretion, has been associated with OT plasma level. The common catechol-O-methyltransferase (COMT) val158met polymorphism is known to influence COMT activity and therefore the degradation of DA. The present study aimed to investigate OT × DA interactions in the context of an OT challenge study. Hence, we tested the influence of the above mentioned genetic variants and their interaction on the activation of different brain regions (amygdala, VTA, ventral striatum and fusiform gyrus) during the presentation of social stimuli. In a pharmacological cross-over design 55 participants were investigated under OT and placebo (PLA) by means of fMRI. Brain imaging results revealed no significant effects for VTA or ventral striatum. Regarding the fusiform gyrus, we could not find any effects apart from those already described in Sauer et al. (2012). Analyses of amygdala activation resulted in no gene main effect, no gene × substance interaction but a significant gene × gene × substance interaction. While under PLA the effect of CD38 on bilateral amygdala activation to social stimuli was modulated by the COMT genotype, no such epistasis effect was found under OT. Our results provide evidence for an OT × DA interaction during responses to social stimuli. We postulate that the effect of central OT secretion on amygdala response is modulated by the availability of DA. Therefore, for an understanding of the effect of social hormones on social behavior, interactions of OT with other transmitter systems have to be taken into account.
Acute physical activity has been repeatedly shown to improve various cognitive functions. However, there have been no investigations comparing the effects of exercise during verbal encoding versus exercise prior to encoding on long-term memory performance. In this current psychoneuroendocrinological study we aim to test whether light to moderate ergometric bicycling during vocabulary encoding enhances subsequent recall compared to encoding during physical rest and encoding after being physically active. Furthermore, we examined the kinetics of brain-derived neurotrophic factor (BDNF) in serum which has been previously shown to correlate with learning performance. We also controlled for the BDNF val66met polymorphism. We found better vocabulary test performance for subjects that were physically active during the encoding phase compared to sedentary subjects. Post-hoc tests revealed that this effect was particularly present in initially low performers. BDNF in serum and BDNF genotype failed to account for the current result. Our data indicates that light to moderate simultaneous physical activity during encoding, but not prior to encoding, is beneficial for subsequent recall of new items.
Identifying moving things in the environment is a priority for animals as these could be prey, predators, or mates. When the shape of a moving object is hard to see, motion becomes an important cue to distinguish animate from inanimate things. We report a new stimulus in which a single moving dot evokes a reasonably strong percept of animacy by mimicking the motion of naturally occurring stimuli, with minimal context information. Stimulus movements are controlled by an equation such that changes in a single movement parameter lead to gradual changes in animacy judgments with minimal changes in low-level stimulus properties. An infinite number of stimuli can be created between the animate and inanimate extremes. A series of experiments confirm the strength of the percept and show that observers tend to follow the stimulus with their eye gaze. However, eye movements are not necessary for perceptual judgments, as forced fixation on the display center only slightly reduces the amplitude of percept changes. Withdrawing attentional resources from the animacy judgment using a simultaneous secondary task further reduces percept amplitudes without abolishing them. This stimulus could open new avenues for the principled study of animacy judgments based on object motion only.
Facial motion carries essential information about other people's emotions and intentions. Most previous studies have suggested that facial motion is mainly processed in the superior temporal sulcus (STS), but several recent studies have also shown involvement of ventral temporal face-sensitive regions. Up to now, it is not known whether the increased response to facial motion is due to an increased amount of static information in the stimulus, to the deformation of the face over time, or to increased attentional demands. We presented nonrigidly moving faces and control stimuli to participants performing a demanding task unrelated to the face stimuli. We manipulated the amount of static information by using movies with different frame rates. The fluidity of the motion was manipulated by presenting movies with frames either in the order in which they were recorded or in scrambled order. Results confirm higher activation for moving compared with static faces in STS and under certain conditions in ventral temporal face-sensitive regions. Activation was maximal at a frame rate of 12.5 Hz and smaller for scrambled movies. These results indicate that both the amount of static information and the fluid facial motion per se are important factors for the processing of dynamic faces.
People often consider how their actions influence others when making decisions. However, we are not equally generous to everyone alike. Our willingness to share resources declines as a function of social distance between the decision maker and the recipient. This function is likely to be influenced by culture, but research on behavioral decision making is still lacking empirical evidence. In Western societies, individuals generally perceive themselves as autonomous and independent from others, whereas the distinction between self and close others is less sharply defined by Eastern individuals where relationships and group membership are more centralized. Therefore, the social discount function should reflect this difference in the distinction of self and others by a reduced decline in generosity over close social distances. A social decision-making task was adapted to the intercultural context, and data were collected in Germany and China. For seven different social distances, we estimated how much money German and Chinese subjects were willing to forego to give a certain reward to another person. A hyperbolic model was fitted to the data. We found that other-regarding generosity declines as a function of social distance independent of cultural identity. However, German subjects showed a marked drop in generosity across close social distances, which was significantly less pronounced in Chinese participants.
This study presents results of the validation of an ultra-short survey measure of patience included in the German Socio-Economic Panel (SOEP). Survey responses predict intertemporal choice behavior in incentive-compatible decisions in a representative sample of the German adult population.
PURPOSE: Limbic encephalitis is an autoimmune-mediated disease leading to temporal lobe epilepsy, mnestic deficits, and affective disturbances. Magnetic resonance imaging (MRI) usually shows signal and volume changes of the temporomesial structures. However, these abnormalities may be subtle, thereby hampering the diagnosis by conventional visual assessment. In the present study we evaluated the diagnostic value of a fully automated MRI postprocessing technique in limbic encephalitis and hippocampal sclerosis. METHODS: The MRI postprocessing was based largely on a recently described method allowing for an observer-independent quantification of the fluid-attenuated inversion recovery (FLAIR) signal intensities of amygdala and hippocampus. A 95% confidence region was calculated from the FLAIR intensities of 100 healthy controls. We applied this analysis to the MRI data of 39 patients with antibody-associated limbic encephalitis and 63 patients with hippocampal sclerosis. Moreover, the results were compared to those of visual assessment by an experienced neuroradiologist. KEY FINDINGS: The method detected limbic encephalitis and hippocampal sclerosis with a high sensitivity of 85% and 95%, respectively. The detection rate of the automated approach in limbic encephalitis was significantly superior to visual analysis (85% vs. 51%; p = 0.001), whereas no statistically significant difference for the detection rate in hippocampal sclerosis was found. Patients with limbic encephalitis had significantly higher absolute intensity values of the amygdala and a significantly higher percentage fell outside of the amygdalar confidence region compared to those with hippocampal sclerosis (79% vs. 27%; p < 0.001), whereas we found opposite results in the hippocampal analysis (38% vs. 95%; p < 0.001). SIGNIFICANCE: The FLAIR analysis applied in this study is a powerful tool to quantify signal changes of the amygdala and hippocampus in limbic encephalitis and hippocampal sclerosis. It significantly increases the diagnostic sensitivity in limbic encephalitis in comparison to conventional visual analysis. Furthermore, the method provides an interesting insight into the distinct properties of these two disease entities on MRI, indicating a predominant affection of the amygdala in limbic encephalitis, whereas the affection of the hippocampus is far less pronounced when compared to hippocampal sclerosis.
2012
Promotions play an important role for the provision of incentives in firms. We analyze incentives in multistage elimination tournaments with controlled laboratory experiments. In our two main treatments, we compare a two-stage tournament to a one-stage tournament. Subjects in the two-stage treatment provide excess effort in the first stage, both with respect to Nash predictions and compared to the strategically equivalent one-stage tournament. Additional control treatments confirm that excess effort in early stages is a robust finding and suggest that above-equilibrium effort might be driven by limited degrees of forward-looking behavior and subjects deriving nonmonetary value from competing.
Although both economists and psychologists seek to identify determinants of heterogeneity in behavior, they use different concepts to capture them. In this review, we first analyze the extent to which economic preferences and psychological concepts of personality, such as the Big Five and locus of control, are related. We analyze data from incentivized laboratory experiments and representative samples and find only low degrees of association between economic preferences and personality. We then regress life outcomes (such as labor market success, health status, and life satisfaction) simultaneously on preference and personality measures. The analysis reveals that the two concepts are rather complementary when it comes to explaining heterogeneity in important life outcomes and behavior.
OBJECTIVE: This study investigates the association between the five-factor model of personality measured by the NEO Five-Factor Inventory (NEO-FFI) and the Overall Assessment of the Speaker's Experience of Stuttering (OASES). The OASES measures the adverse impact of stuttering on a person's life. DESIGN: Participants in the present study were 112 persons who stutter from Germany. METHODS: All participants filled in both the NEO-FFI and the OASES questionnaires. RESULTS: Results revealed a strong positive correlation between the personality trait Neuroticism and scores on the OASES. Moreover, Extraversion was negatively correlated with the OASES scores. CONCLUSIONS: The findings suggest that people with higher Neuroticism and lower Extraversion scores experience a greater impact of stuttering on their daily life. The results underscore the importance of considering personality as a potential moderator or mediator factor in future stuttering research and, potentially, also in treatment. EDUCATIONAL OBJECTIVES: The reader will learn (a) about the different personality dimensions reflected by the NEO-FFI, (b) why it is important to consider the impact of stuttering on everyday life from the perspective of the people who stutter and (c) how personality is linked to the Overall Assessment of the Speaker's Experience of Stuttering (OASES).
When workers are faced with the threat of unemployment, their relationship with a particular firm becomes valuable. As a result, a worker may comply with the terms of a relational contract that demands high effort even when performance is not enforceable by a third party. But can relational contracts motivate high effort when workers can easily find alternative jobs? We examine how competition for labor affects the emergence of relational contracts and their effectiveness in overcoming moral hazard in the labor market. We show that effective relational contracts do emerge in a market with excess demand for labor. Long-term relationships turn out to be less frequent when there is excess demand for labor than they are in a market characterized by exogenous unemployment. However, stronger competition for labor does not impair labor market efficiency: higher wages induced by competition lead to higher effort out of concerns for reciprocity.
BACKGROUND: One of the most widely studied genetic polymorphisms regarding cognitive and emotional phenotypes is the COMT Val158Met polymorphism that influences dopamine availability in the prefrontal cortex (PFC). The PFC is the key brain structure for higher cognitive functions such as working memory, as well as an important regulatory site and target of the psychoendocrine stress response. Dopamine is thought to influence PFC functions in an inverted u-shaped manner. Thus, a stress-related increase in prefrontal dopamine is hypothesized to exert differential effects on working memory performance depending on the genetically determined baseline dopamine level in the PFC. METHOD: Thirty-three healthy young subjects homozygous for the COMT Val158Met polymorphism were selected from a larger pre-genotyped sample. They performed an n-back working memory task after exposure to a laboratory psychosocial stress induction paradigm (The Trier Social Stress Test for Groups; TSST-G). RESULTS: Under stress, working memory performance of Met homozygotes was significantly worse than working memory performance of Val homozygotes. Importantly, this genotype effect was restricted to the medium difficulty level of the n-back task. CONCLUSION: Our results demonstrate that working memory performance under stress is influenced by genetic variation in prefrontal dopamine levels. More generally, our results point to the importance of considering the complex interaction of genes, environment, and task variables.
This article discusses the role of commonly used neurophysiological tools such as psychophysiological tools (e.g., EKG, eye tracking) and neuroimaging tools (e.g., fMRI, EEG) in Information Systems research. There is heated interest now in the social sciences in capturing presumably objective data directly from the human body, and this interest in neurophysiological tools has also been gaining momentum in IS research (termed NeuroIS). This article first reviews commonly used neurophysiological tools with regard to their major strengths and weaknesses. It then discusses several promising application areas and research questions where IS researchers can benefit from the use of neurophysiological data. The proposed research topics are presented within three thematic areas: (1) development and use of systems, (2) IS strategy and business outcomes, and (3) group work and decision support. The article concludes with recommendations on how to use neurophysiological tools in IS research along with a set of practical suggestions for developing a research agenda for NeuroIS and establishing NeuroIS as a viable subfield in the IS literature.
We present an economic experiment on network formation, in which subjects can decide to form links to one another. Direct links are costly but being connected is valuable. The game-theoretic basis for our experiment is the model of Bala and Goyal (2000). They distinguish between two scenarios regarding the flow of benefits through a network, the so-called 1-way and 2-way flow model. Our main results show that the prediction based on Nash and strict Nash equilibrium works well in the 1-way flow model but fails largely in the 2-way flow model. We observe a strong learning dynamic in the 1-way flow model but less so in the 2-way flow model. Finally, costs of a direct link have a positive impact on the occurrence of (strict) Nash networks in the 1-way flow model but a negative impact in the 2-way flow model. In our discussion on possible explanations for these results we focus on strategic asymmetry and asymmetry with respect to payoffs. We find that the latter asymmetry, i.e., payoff inequity, plays an important role in the network formation process.
In this paper we study neural responses to inequitable distributions of rewards despite equal performance. We specifically focus on differences between advantageous inequity (AI) and disadvantageous inequity (DI). AI and DI were realized in a hyperscanning functional magnetic resonance imaging (fMRI) experiment with pairs of subjects simultaneously performing a task in adjacent scanners and observing both subjects' rewards. Results showed (1) hypoactivation of the ventral striatum (VS) under DI but not under AI; (2) inequity induced activation of the right dorsolateral prefrontal cortex (DLPFC) that was stronger under DI than under AI; (3) correlations between subjective evaluations of AI evaluation and bilateral ventrolateral prefrontal and left insular activity. Our study provides neurophysiological evidence for different cognitive processes that occur when exposed to DI and AI, respectively. One possible interpretation is that any form of inequity represents a norm violation, but that important differences between AI and DI emerge from an asymmetric involvement of status concerns.
Behaviourally, humans have been shown to integrate multisensory information in a statistically-optimal fashion by averaging the individual unisensory estimates according to their relative reliabilities. This form of integration is optimal in that it yields the most reliable (i.e. least variable) multisensory percept. The present study investigates the neural mechanisms underlying integration of visual and tactile shape information at the macroscopic scale of the regional BOLD response. Observers discriminated the shapes of ellipses that were presented bimodally (visual-tactile) or visually alone. A 2. × 5 factorial design manipulated (i) the presence vs. absence of tactile shape information and (ii) the reliability of the visual shape information (five levels). We then investigated whether regional activations underlying tactile shape discrimination depended on the reliability of visual shape. Indeed, in primary somatosensory cortices (bilateral BA2) and the superior parietal lobe the responses to tactile shape input were increased when the reliability of visual shape information was reduced. Conversely, tactile inputs suppressed visual activations in the right posterior fusiform gyrus, when the visual signal was blurred and unreliable. Somatosensory and visual cortices may sustain integration of visual and tactile shape information either via direct connections from visual areas or top-down effects from higher order parietal areas.
The neurophysiological mechanisms underlying superior cognitive performance are a research area of high interest. The majority of studies on the brain-performance relationship assessed the effects of capability-related group factors (e.g. talent, gender) on task-related brain activations while only few studies examined the effect of the inherent experimental task performance factor. In this functional MRI study, we combined both approaches and simultaneously assessed the effects of three relatively independent factors on the neurofunctional correlates of mental rotation in same-aged adolescents: math talent (gifted/controls: 17/17), gender (male/female: 16/18) and experimental task performance (median split on accuracy; high/low: 17/17). Better experimental task performance of mathematically gifted vs. control subjects and male vs. female subjects validated the selected paradigm. Activation of the inferior parietal lobule (IPL) was identified as a common effect of mathematical giftedness, gender and experimental task performance. However, multiple linear regression analyses (stepwise) indicated experimental task performance as the only predictor of parietal activations. In conclusion, increased activation of the IPL represents a positive neural correlate of mental rotation performance, irrespective of but consistent with the obtained neurocognitive and behavioral effects of math talent and gender. As experimental performance may strongly affect task-related activations this factor needs to be considered in capability-related group comparison studies on the brain-performance relationship.
BACKGROUND: In patients with temporal lobe epilepsy and associated hippocampal sclerosis (TLEhs) there are brain abnormalities extending beyond the presumed epileptogenic zone as revealed separately in conventional magnetic resonance imaging (MRI) and MR diffusion tensor imaging (DTI) studies. However, little is known about the relation between macroscopic atrophy (revealed by volumetric MRI) and microstructural degeneration (inferred by DTI). METHODOLOGY/PRINCIPAL FINDINGS: For 62 patients with unilateral TLEhs and 68 healthy controls, we determined volumes and mean fractional anisotropy (FA) of ipsilateral and contralateral brain structures from T1-weighted and DTI data, respectively. We report significant volume atrophy and FA alterations of temporal lobe, subcortical and callosal regions, which were more diffuse and bilateral in patients with left TLEhs relative to right TLEhs. We observed significant relationships between volume loss and mean FA, particularly of the thalamus and putamen bilaterally. When corrected for age, duration of epilepsy was significantly correlated with FA loss of an anatomically plausible route – including ipsilateral parahippocampal gyrus and temporal lobe white matter, the thalamus bilaterally, and posterior regions of the corpus callosum that contain temporal lobe fibres – that may be suggestive of progressive brain degeneration in response to recurrent seizures. CONCLUSIONS/SIGNIFICANCE: Chronic TLEhs is associated with interrelated DTI-derived and volume-derived brain degenerative abnormalities that are influenced by the duration of the disorder and the side of seizure onset. This work confirms previously contradictory findings by employing multi-modal imaging techniques in parallel in a large sample of patients.
The present study investigates for the first time the influence of the DRD2 C957T polymorphism on personality in persons who stutter. In a recent study, the CC genotype of this single nucleotide polymorphism has been associated with stuttering, which could not be replicated in a follow-up study. Here, we demonstrate, in N=105 persons who stutter, that carriers of the CC and the CT genotype significantly have the highest neuroticism scores. This shows that the inclusion of personality measures in the investigation of the biological underpinnings of stuttering represents an important new avenue. In healthy control persons, a sex by C+/- allele interaction effect could be demonstrated. Female but not male carriers of the C+ variant report the highest neuroticism scores. Because neuroticism has been reported to be associated with stuttering before, the present data support the idea that this personality trait acts as an endophenotype for stuttering, contributing towards bridging the gap from gene variation to the complex pathology. This idea is supported by an additional path model showing that the polymorphism DRD2 C957T influences the self-reported severity of stuttering mainly by its influence on neuroticism (independent of the variable sex).
The temporal lobe plays a major role in anxiety and depression disorders and is also of importance for trait anxiety in the non-pathological range. The present study investigates self-report data of personality dimensions linked to trait anxiety in the context of white matter tract integrity in the temporal lobes of the human brain in a large sample of N=110 healthy participants. The results show that especially in men values for fractional anisotropy of several white matter tracts in the temporal lobe of the left hemisphere correlate substantially with individual differences in trait anxiety (depending on the tract investigated between .40 and .49). The present study shows that not only data from functional magnetic resonance imaging (fMRI), but also from structural diffusion tensor imaging (DTI) provide interesting insights into the biological foundation of human personality traits.
The present case-control study investigated the processing of emotional pictures in excessive first-person-shooter-video-players and control persons. All participants of the fMRI experiment were confronted with pictures from four categories including pleasant, unpleasant, neutral content and pictures from the first-person-shooter-video-game 'Counterstrike'. Compared to controls, gamers showed a significantly lower activation of the left lateral medial frontal lobe while processing negative emotions. Another interesting finding of the study represents the higher activation of frontal and temporal brain areas in gamers when processing screen-shots from the first-person-shooter-video-game 'Counterstrike'. Higher brain activity in the lateral prefrontal cortex could represent a protection mechanism against experiencing negative emotions by down-regulating limbic brain activity. Due to a frequent confrontation with violent scenes, the first-person-shooter-video-gamers might have habituated to the effects of unpleasant stimuli resulting in lower brain activation. Individual differences in brain activations of the contrast Counterstrike > neutral pictures potentially resemble the activation of action-scripts related to the video-game.
The current study investigates the whole brain myelin water content distribution applying a new approach that allows for the simultaneous mapping of total and relative myelin water content, T 1 and T 2* with full brain coverage and high resolution (1 × 1 × 2 mm(3)). The data was collected at two different sites in healthy controls to validate the independence of a specific setup. In addition, a group of patients with known white matter affections was investigated to compare two measures of myelin, i.e. relative and absolute myelin water content. Based on the first dataset, a quantitative myelin water content atlas was created which served as a control set for the other two datasets. Both control groups measured at different institutions yielded consistent results. However, distinct regions of reduced myelin water content were observed for the patient dataset, both on an individual basis and in a group-wise comparison. The comparison between the absolute and relative measurement of myelin water content in MS patients showed that the relative measurement, which is employed by many researchers, overestimates both disease volume and the corresponding reduction of myelin water content in white matter lesions. However, for normal appearing white matter, no difference between both approaches was detected. The results obtained in the current study demonstrate that absolute myelin water content can reliably be determined in a multicentre environment using standard MR sequences. The optimised protocol allows for a measurement of four quantitative parameters with full brain coverage in only 10 min. This might expedite a more widespread future use of quantitative MRI methods for clinical research and diagnosis.
This is the first study to combine psychometric and functional neuroimaging methods to study altered patterns ofautobiographical memory in bipolar disorder (BD). All participants were interviewed with an expanded version of the Bielefelder Autobiographical Memory Inventory (Bielefelder Autobiographisches Geda¨chtnis Inventar 2004;Lisse: Swets and Zeitlinger). We then acquired functional magnetic resonance imaging data during a task of individually designed autobiographical recall. Compared with healthy con- trols, BD patients reported a stronger emotionality of autobiographical mem- ories and more frequent recollections of autobiographical events during their everyday life. Furthermore, they failed to deactivate areas in the cuneus and lingual gyrus and showed decreased activation in the inferior frontal and pre- central areas compared with the control group. More frequent intrusions from a person’s past, which had a neural correlate in the lack of deactivation in some default mode network areas in BD patients, may contribute to manic or depressive symptoms.
Evidence supports the involvement of oxytocin in social behavior. The oxytocin receptor gene (OXTR) has been associated with differences in social brain function and risk for autism. Motivated by recent work, we investigated the effect of variation in the common functional rs2268498 T/C polymorphism in the promoter region of OXTR on neural responses to fear expressions. 46 healthy subjects were divided into genotype groups of C carriers (n = 32) and TT homozygous (n = 14) and neural activity was measured during the recognition of fear and neutral expressions. Results showed that during the recognition of fear expressions, the TT genotype group exhibited increased responding in the inferior occipital gyrus, considered important for face processing, compared to carriers of the C allele (P < 0.005; cluster corrected for whole brain), an effect not found for neutral faces. These results indicate the impact of this OXTR genetic variant on individual differences in social affective neural processing.
Chronic stress and related disruption of hypothalamic-pituitary-adrenal axis reactivity is a known risk factor for depression. Besides its effects on glucocorticoids, stress also impacts the cholinergic system. Therefore, the interaction of two polymorphisms, one on the cholinergic CHRNA4 receptor gene and one on the glucocorticoid receptor gene (NR3C1), on depression was investigated. In a sample of 800 healthy participants, we genotyped for the BCL1 rs41423247 and the CHRNA4 rs1044396 single-nucleotide polymorphisms and assessed depressiveness by means of the Beck Depression Inventory. We identified a significant epistasis effect BCL1 by CHRNA4 showing that carriers of the CC genotype at the BCL1 locus who were also homozygous for the T allele at the CHRNA4 locus had the highest depression scores. This is the first evidence from molecular genetics to show that the hypothalamic-pituitary-adrenal axis and the cholinergic system – both involved in stress reactivity – represent a combined risk factor for depression.
The representation of reward anticipation and reward prediction errors is the basis for reward-associated learning. The representation of whether or not a reward occurred (reward receipt) is important for decision making. Recent studies suggest that, while reward anticipation and reward prediction errors are encoded in the midbrain and the ventral striatum, reward receipts are encoded in the medial orbitofrontal cortex. In order to substantiate this functional specialization we analyzed data from an fMRI study in which 59 subjects completed two simple monetary reward paradigms. Because reward receipts and reward prediction errors were correlated, a statistical model comparison was applied separating the effects of the two. Reward prediction error fitted BOLD responses significantly better than reward receipt in the midbrain and the ventral striatum. Conversely, reward receipt fitted BOLD responses better in the orbitofrontal cortex. Activation related to reward anticipation was found in the orbitofrontal cortex. The results confirm a functional specialization of behaviorally important aspects of reward processing within the mesolimbic dopaminergic system.
Individual risk preferences have a large influence on decisions, such as financial investments, career and health choices, or gambling. Decision making under risk has been studied both behaviorally and on a neural level. It remains unclear, however, how risk attitudes are encoded and integrated with choice. Here, we investigate how risk preferences are reflected in neural regions known to process risk. We collected functional magnetic resonance images of 56 human subjects during a gambling task (Preuschoff et al., 2006). Subjects were grouped into risk averters and risk seekers according to the risk preferences they revealed in a separate lottery task. We found that during the anticipation of high-risk gambles, risk averters show stronger responses in ventral striatum and anterior insula compared to risk seekers. In addition, risk prediction error signals in anterior insula, inferior frontal gyrus, and anterior cingulate indicate that risk averters do not dissociate properly between gambles that are more or less risky than expected. We suggest this may result in a general overestimation of prospective risk and lead to risk avoidance behavior. This is the first study to show that behavioral risk preferences are reflected in the passive evaluation of risky situations. The results have implications on public policies in the financial and health domain.
The intranasal application of oxytocin (OT) has been shown to influence behavioral and neural correlates of social processing. These effects are probably mediated by genetic variations within the OT system. One potential candidate could be the CD38 gene, which codes for a transmembrane protein engaged in OT secretion processes. A common variation in this gene (rs3796863) was recently found to be associated with autism spectrum disorders (ASD). Using an imaging genetics approach, we studied differential effects of an intranasal OT application on neural processing of social stimuli in 55 healthy young men depending on their CD38 gene variant in a double-blind placebo-controlled crossover design. Genotype had a significant influence on both behavioral and neuronal measures of social processing. Homozygotic risk allele carriers showed slower reaction times (RT) and higher activation of left fusiform gyrus during visual processing of social stimuli. Under OT activation differences between genotypes were more evident (though not statistically significantly increased) and RT were accelerated in homozygotic risk allele carriers. According to our data, rs3796863 mainly influences fusiform gyrus activation, an area which has been widely discussed in ASD research. OT seems to modulate this effect by enhancing activation differences between allele groups, which suggests an interaction between genetic makeup and OT availability on fusiform gyrus activation. These results support recent approaches to apply OT as a pharmacological treatment of ASD symptoms.
Purpose: Rasmussen encephalitis is a chronic immune‐mediated disease leading to unilateral atrophy on magnetic resonance imaging (MRI) and progressive neurologic deficits. Until now, quantitative parameters describing the course of the disease on MRI require manual intervention and are, therefore, time‐consuming and observer‐dependent. Furthermore, regional atrophy differences cannot be evaluated with the previously published methods. In this study we present a fully automated volumetric approach applied to serial MRI scans of 12 patients with Rasmussen encephalitis.
Methods: We retrospectively analyzed 12 patients with Rasmussen encephalitis with a disease onset between 2001 and 2008. All patients underwent a total of 66 serial MRI scans including a three‐dimensional T1 data set. The volumetric analysis was based on standard procedures of the freely available software FMRIB Software Library (FSL) and required about 45 min per scan. Furthermore, planimetric analyses were performed on 51 scans as described previously.
Key Findings: The relative and absolute volume loss of the affected hemisphere was significantly higher compared to the unaffected hemisphere. Referring to regional atrophy differences our results show that the frontal lobe and the insula were preferentially involved in the atrophic process. The degree of hemispheric, parietal, and occipital atrophy was negatively correlated with the age at disease onset, indicating a more aggressive and outspread disease in young children compared to adolescents. Volumetric hemispheric ratio and planimetric hemispheric ratio correlated significantly, but planimetric hemispheric ratio underestimated the real degree of hemiatrophy, especially in patients with predominant affections outside the frontoinsular region.
Significance: The volumetric analysis presented here offers a precise assessment of the disease progression in Rasmussen encephalitis in an observer‐independent and time‐efficient manner and gives an interesting insight into the course of the disease on MRI. The degree of atrophy evaluated with this method correlates with clinical parameters and is comparable to atrophy rates in patients receiving immunotherapy in preceding planimetric MRI studies.
Perspective-taking has become a main focus of studies on moral judgments. Recent fMRI studies have demonstrated that individual differences in brain activation predict moral decision making. In particular, pharmacological studies highlighted the crucial role for the neuropeptide oxytocin in social behavior and emotional perception. In the present study N=154 participants were genotyped for a functional polymorphism (rs2268498) in the promoter region of the OXTR gene. We found a significant difference between carriers and non-carriers of the C-allele in exculpating agents for accidental harms (F((1,152))=11.49, p=.001, η(2)=.07) indicating that carriers of the C-allele rated accidentally committed harm as significantly more blameworthy than non-carriers. This is the first study providing evidence for a genetic contribution to moral judgments.
Olivier Oullier questions the commercial and judicial use of brain-scan technology to predict or judge human behaviour (Nature 483, 7; 2012). His arguments undermine a major driver of academic funding and research — its potential for commercial application. Moreover, banning the commercial use of neuroimaging could encourage government interference in the development of a promising and widely applicable tool.
Lying is a pervasive phenomenon with important social and economic implications. However, despite substantial interest in the prevalence and determinants of lying, little is known about its biological foundations. Here we study a potential hormonal influence, focusing on the steroid hormone testosterone, which has been shown to play an important role in social behavior. In a double-blind placebo-controlled study, 91 healthy men (24.3262.73 years) received a transdermal administration of 50 mg of testosterone (n=46) or a placebo (n=45). Subsequently, subjects participated in a simple task, in which their payoff depended on the self-reported outcome of a die-roll. Subjects could increase their payoff by lying without fear of being caught. Our results show that testosterone administration substantially decreases lying in men. Self- serving lying occurred in both groups, however, reported payoffs were significantly lower in the testosterone group (p,0.01). Our results contribute to the recent debate on the effect of testosterone on prosocial behavior and its underlying channels.
2011
In this paper, we discuss recent evidence from economic experiments that study the impact of social preferences on workplace behavior. We focus on situations in which a single employer interacts with multiple employees. Traditionally, equity and efficiency have been seen as opposing aims in such work environments: individual pay-for-performance schemes maximize efficiency but might lead to inequitable outcomes. We present findings from laboratory experiments that show under which circumstances partially incomplete contracts can create equitable work environments while at the same time reaching surprisingly efficient outcomes.
A key open question for theories of reference-dependent preferences is: what determines the reference point? One candidate is expectations: what people expect could affect how they feel about what actually occurs. In a real-effort experiment, we manipulate the rational expectations of subjects and check whether this manipulation influences their effort provision. We find that effort provision is significantly different between treatments in the way predicted by models of expectation-based, reference-dependent preferences: if expectations are high, subjects work longer and earn more money than if expectations are low.
People have present-biased preferences: they choose more impatiently when choosing between an immediate reward and a delayed reward, than when choosing between a delayed reward and a more delayed reward. Following McClure et al. [McClure, S.M., Laibson, D.I., Loewenstein, G., Cohen, J.D. (2004). Separate neural systems value immediate and delayed monetary rewards. Science, 306, 503.], we find that areas in the dopaminergic reward system show greater activation when a binary choice set includes both an immediate reward and a delayed reward in contrast to activation measured when the binary choice set contains only delayed rewards. The presence of an immediate reward in the choice set elevates activation of the ventral striatum, pregenual anterior cingulate cortex and anterior medial prefrontal cortex. These dopaminergic reward areas are also responsive to the identity of the recipient of the reward. Even an immediate reward does not activate these dopaminergic regions when the decision is being made for another person. Our results support the hypotheses that participants show less affective engagement (i) when they are making choices for themselves that only involve options in the future or (ii) when they are making choices for someone else. As hypothesized, we also find that behavioral choices reflect more patience when choosing for someone else.
Die Präzision ökonomischer Prognosen und die Qualität politischer Handlungsempfehlungen hängen in entscheidendem Ausmaß von der Qualität des zugrunde liegenden Verhaltensmodells ab. Nur ein empirisch gut fundiertes Modell ökonomischen Handelns erlaubt es, die Konsequenzen politischer Maßnahmen präzise abzuschätzen. In der wirtschaftswissenschaftlichen Analyse ist das Konzept des Homo Oeconomicus als Entscheidungs- und Verhaltensmodell weit verbreitet. Empirische Ergebnisse aus der Verhaltensökonomik legen jedoch zwei grundsätzliche Abweichungen vom traditionellen Modell des Homo Oeconomicus nahe: Abweichungen vom Prinzip der uneingeschränkten Rationalität einerseits und die Infragestellung einer universellen Eigennutzorientierung andererseits. Die vorliegende Arbeit gibt einen Überblick über ausgewählte, wirtschaftspolitisch bedeutsame Abweichungen vom Rationalitätspostulat. Anschließend diskutieren wir am Beispiel so genannter „nicht bindender Defaultoptionen“, weshalb für eingeschränkt rationale Akteure politische Maßnahmen oder rechtliche Regelungen auch dann Verhaltenskonsequenzen haben können, wenn diese aus rationaler Sichtweise nicht zu erwarten wären und möglicherweise durch den Gesetzgeber auch nicht beabsichtigt sind. Abschließend stellen wir dar, wie nicht bindende Defaults selbst als Politikinstrument eingesetzt werden können: klug gewählt können sie dabei helfen, Entscheidungen zu verbessern ohne dabei individuelle Wahlfreiheit einzuschränken.
A recent study by Iverach et al. (Journal of Communication Disorders, 2010) compared persons who stutter with two normative samples in the context of the five-factor model of personality measured by the NEO Five-Factor Inventory (NEO-FFI). Persons who stutter were characterized by higher Neuroticism, lower Conscientiousness and lower Agreeableness scores in contrast to the normative data from an Australian and a United States sample. Moreover, the authors report that the scores on all five personality dimensions in the stuttering group were within those of the normative samples. A shortcoming of the Iverach et al. study is the lack of a matched control group. In the present study we compared persons who stutter with a control group matched to age and gender. Furthermore, none of the controls had a history of personal and family stuttering. The findings with respect to Neuroticism could be replicated in our sample. But in contrast to Iverach et al. we found higher Conscientiousness and Agreeableness scores in persons who stutter compared to the control group.
Learning outcomes: The reader of the present study will learn that elevated Neuroticism scores can be observed in persons who stutter across cultures such as Germany or Australia. With respect to other personality dimensions such as Conscientiousness or Agreeableness the picture is much more difficult.
The evaluation of labor market policies has become an important issue in many European countries. In recent years, a number of them have opened their administrative databases for evaluation studies. The advantages of administrative data are straightforward: they are accurate, contain a large number of observations (in some cases the whole population) and usually cover a long period of time. However, the information contained in administrative data is normally limited to administrative purposes. Therefore, information that might be relevant for economic modeling is often absent. The IZA Evaluation Dataset aims to overcome such limitations for Germany by complementing administrative data from the Federal Employment Agency with innovative survey data. The administrative part of the dataset consists of a large random sample of inflows into unemployment in Germany from 2001 to 2008 and contains around 920,000 individuals. The complementary survey covers a panel of more than 17,000 individuals who entered unemployment between June 2007 and May 2008. They were initially interviewed shortly after becoming unemployed and then again one year later. In addition, a quarter of individuals were interviewed already after six months. The survey data also contain information on search behavior, ethnic and social networks, psychological factors, (non-)cognitive abilities, and attitudes. This paper describes the sampling and contents of the IZA Evaluation Dataset and outlines the future development.
This paper studies the impact of incentives on worker self-selection in a controlled laboratory experiment. Subjects face the choice between a fixed and a variable payment scheme. Depending on the treatment, the variable payment is a piece rate, a tournament, or a revenue-sharing scheme. We find that output is higher in the variable-payment schemes compared to the fixed-payment scheme. This difference is largely driven by productivity sorting. In addition, different incentive schemes systematically attract individuals with different attitudes, such as willingness to take risks and relative self-assessment as well as gender, which underlines the importance of multidimensional sorting.
In this paper we study the role of absolute versus relative income using functional magnetic resonance imaging (fMRI). While being scanned in two adjacent MRI scanners, pairs of subjects had to simultaneously perform a simple estimation task that entailed monetary rewards for correct answers. We show that a variation in the comparison subject's payment affects blood oxygenation level-dependent (BOLD) responses in the ventral striatum. This brain region is engaged in the prediction and registration of primary rewards such as food delivery as well as more abstract forms of rewards like money. In particular, we show that activation in the ventral striatum increases in absolute income and – for a given level of absolute income – decreases in lower relative income. Using a male and a female sample allows us to study whether the perception of relative and absolute incomes is gender specific. We find that the effects of absolute and relative incomes are strong and relatively similar for both genders. Finally, we analyze the importance of “joy of winning”, i.e., the impact of outperforming another subject. Our results suggest that the mere fact of outperforming the other subject positively affects reward related brain areas.
Recent theories endogenize the attitude endowments of individuals, assuming that they are shaped by the attitudes of parents and other role models. This paper tests empirically for the relevance of three aspects of the attitude transmission process highlighted in this theoretical literature: (1) transmission of attitudes from parents to children; (2) an impact of prevailing attitudes in the local environment on child attitudes; and (3) positive assortative mating of parents, which enhances the ability of a parent to pass on his or her attitudes to the child. We focus on two fundamentally important attitudes, willingness to take risks and willingness to trust others. We find empirical support for all three aspects, providing an empirical underpinning for the literature. An investigation of underlying mechanisms shows that socialization is important in the transmission process. Various parental characteristics and aspects of family structure are found to strengthen the socialization process, with implications for modeling the socialization production function and for policies focused on affecting children's non-cognitive skills. The paper also provides evidence that the transmission of risk and trust attitudes affects a wide variety of child outcomes, implying a potentially large total effect on children's economic situation.
This paper studies risk attitudes using a large representative survey and a complementary experiment conducted with a representative subject pool in subjects’ homes. Using a question asking people about their willingness to take risks “in general”, we find that gender, age, height, and parental background have an economically significant impact on willingness to take risks. The experiment confirms the behavioral validity of this measure, using paid lottery choices. Turning to other questions about risk attitudes in specific contexts, we find similar results on the determinants of risk attitudes, and also shed light on the deeper question of stability of risk attitudes across contexts. We conduct a horse race of the ability of different measures to explain risky behaviors such as holdings stocks, occupational choice, and smoking. The question about risk taking in general generates the best all-round predictor of risky behavior.
It is frequently argued that unemployment plays a crucial role in the occurrence of right-wing extremist crimes (RECs). We test this hypothesis empirically using data from Germany. We find that right-wing criminal activities occur more frequently when unemployment is high. The substantial difference in the numbers of RECs occurring in the East and West German states can mostly be attributed to differences in unemployment. This finding reinforces the importance of unemployment as an explanatory factor for RECs, and it questions explanations based solely on the different socialization in former communist East Germany and the liberal West German states.
Although prominent personality theories postulate orthogonality between traits of positive emotionality (PEM) and negative emotionality (NEM), empirical evidence often demonstrates the opposite indicating a negative relationship. Therefore, it is not surprising that dopaminergic (DA) gene loci have been related to traits of positive and of NEM. The present genetic association study investigates the influence of two functional DA gene polymorphisms on Sadness as defined by the Affective Neuroscience Personality Scales (ANPS) in healthy Caucasians (n = 1041). We observed a significant interaction effect between the 10-repeat (10R) allele of the dopamine transporter (DAT1) gene and the methionine (Met) allele of the catechol-O-methyltransferase (COMT) Val158Met polymorphism (F((1,1018)) = 11.11; P < 0.001). Carriers of the 9R/9R and the Val/Val genotype showed dramatically reduced Sadness scores in comparison to the other three genotype configurations. Both the 9R/9R and the Val/Val genotypes characterized by reduced transporter density and high dopamine catabolism, respectively, have been separately related to personality traits of PEM and externalizing behavior in the past. The present findings indicate that gene variations of the DA system previously associated with PEM are at the same time protective against high NEM and can therefore constitute a resilience factor against depression.
Deeper semantic processing improves memory encoding of words. Neuroimaging studies suggest, that left-hemispheric structures, especially the left inferior frontal cortex and the left hippocampus mediate this effect. Therefore, we tested, whether chronic left hippocampal damage in epilepsy patients after selective amygdalohippocampectomy (SAH) diminishes the depth-of-processing effect in an incidental learning task. 16 patients after left SAH, 17 after right SAH and 15 healthy control subjects elaborated on word classification tasks under a non-semantic and two different semantic conditions. Recognition memory for the words was subsequently tested. Although memory in left SAH patients profited less from deeper semantic processing in terms of an absolute increase in the number of recognized words, the relative level of memory impairment compared to the two other groups was identical under the non-semantic and the semantic conditions. The results indicate that chronic left hippocampal damage affects recognition memory largely independent of semantic processing.
We analyze two team settings in which one member in a team has stronger incentives to contribute than the others. If contributions constitute a sacrifice for the strong player, the other team members are more inclined to cooperate than if contributions are strictly dominant for the strong player.
The aim of this functional magnetic resonance imaging (fMRI) study was to investigate the correlation between the severity of malocclusion and brain activation. The fMRI was used to measure blood-oxygenation- level-dependent (BOLD) signals of twelve healthy human subjects while they clenched in two different ways to simulate two types of malocclusion. In each malocclusion model, a custom-made splint forced the mandible to each of two retrusive positions (0.5 mm, 0.7 mm). A no-modification splint provided the control. We compared the BOLD signals measured at each clenching position with those measured during the corresponding resting conditions. The BOLD signals were significantly stronger in the amygdala and the prefrontal area (PFA) when subjects clenched in the two retrusive positions compared during clenching in the control position. In addition, the BOLD signal in the PFA increased as the simulated malocclusion became more severe. These results indicate that we may be able to objectively assess the severity of malocclusion via focus on the brain activity.
PURPOSE: To describe and evaluate a novel MRI post-processing technique for automated quantitative hippocampal FLAIR analysis in patients with hippocampal sclerosis (HS). PATIENTS AND METHODS: Based on a method for FLAIR analysis presented by Focke et al. (2009), T1 and coregistered FLAIR scans of individual subjects were processed together in SPM5 to conduct both a spatial and an intensity normalization of the FLAIR scans. In a further development described here, the resulting normalized FLAIR images were thresholded and weighted by a probabilistic hippocampal mask to determine the average FLAIR intensities of left and right hippocampus. The method was applied to the MRI data of 103 HS patients and 131 controls. Using a 95% confidence region calculated from the FLAIR intensities of controls as threshold, the performance in discriminating both groups was assessed. RESULTS: One hundred of 103 patients and among those all 23 patients with histologically confirmed HS fell outside the 95% confidence region, amounting to 97.1% sensitivity. All but 6 controls (=95.4%) were found within the confidence region, corresponding to the expected specificity. The method could also distinguish bilateral HS and visualize signal changes after status epilepticus. CONCLUSION: Automated FLAIR analysis is a promising tool to quantify hippocampal signal alterations, to support the detection of HS, and to monitor the temporal evolution of the disease.
Childhood onset of epilepsy has long been associated with an adverse impact on brain development and cognition. In this study it is proposed that earlier (vs later) onset of temporal lobe epilepsy (TLE) has a negative developmental impact on distant brain structures. One hundred ten patients with TLE were assigned to early (≤14 years, N=58) and late (>15 years, N=52) age at onset of epilepsy groups. Voxel-based morphometry revealed onset-dependent abnormalities (in terms of a gray matter excess in the early-onset group), which were found mainly in frontal regions. An excess of gray matter is not a usual finding in TLE. However, within a neurodevelopmental framework, retained gray matter is discussed as reflecting neurodevelopmental disruption. The findings indicate the importance of quantitative MRI for the detection of subtle secondary abnormalities in focal TLE and once more underline the importance of early seizure management in children with intractable TLE.
Although legal sanctions are often nondeterrent, we frequently observe compliance with “mild laws.” A possible explanation is that the incentives to comply are shaped not only by legal, but also by social sanctions. This paper employs a novel experimental approach to study the link between legal and social norm enforcement. We analyze whether the two institutions are complements or substitutes. Our results show that legal sanctions partially crowd out social norm enforcement. Mild laws nevertheless give scope for a potentially large, positive welfare effect, as a higher level of compliance is achieved at lower social enforcement costs.
BACKGROUND: Transfer entropy (TE) is a measure for the detection of directed interactions. Transfer entropy is an information theoretic implementation of Wiener's principle of observational causality. It offers an approach to the detection of neuronal interactions that is free of an explicit model of the interactions. Hence, it offers the power to analyze linear and nonlinear interactions alike. This allows for example the comprehensive analysis of directed interactions in neural networks at various levels of description. Here we present the open-source MATLAB toolbox TRENTOOL that allows the user to handle the considerable complexity of this measure and to validate the obtained results using non-parametrical statistical testing. We demonstrate the use of the toolbox and the performance of the algorithm on simulated data with nonlinear (quadratic) coupling and on local field potentials (LFP) recorded from the retina and the optic tectum of the turtle (Pseudemys scripta elegans) where a neuronal one-way connection is likely present. RESULTS: In simulated data TE detected information flow in the simulated direction reliably with false positives not exceeding the rates expected under the null hypothesis. In the LFP data we found directed interactions from the retina to the tectum, despite the complicated signal transformations between these stages. No false positive interactions in the reverse directions were detected. CONCLUSIONS: TRENTOOL is an implementation of transfer entropy and mutual information analysis that aims to support the user in the application of this information theoretic measure. TRENTOOL is implemented as a MATLAB toolbox and available under an open source license (GPL v3). For the use with neural data TRENTOOL seamlessly integrates with the popular FieldTrip toolbox.
A growing number of studies in exploring empathic modulation have revealed the neural substrates of how social stimuli are represented in the human brain, especially the pain of others. The empathic response of observing other's gains and losses, however, remains not clearly characterized. In the current study, we carried out two experiments with a gamble task to investigate how the effects of interpersonal familiarity and self-participation work on modulating the temporal neural response towards gain and loss of a friend or a stranger using scalp-recorded event-related potentials (ERPs). The electrophysiological data show an increased amplitude of the P300 when observing a friend's performance compared to strangers playing the game in both two experiments. But the distinction of differentiated feedback-related negativity (d-FRN) between friends and strangers was only observed when the player was not involved in the game. These results indicated that the participants exerted more motivational relevance toward their friends than strangers, but the participants' empathic response toward friends was only salient when they were not involved in the gamble directly. Therefore, both familiarity and self-engagement are factors that influence the empathy towards others, complementing the recent research on empathic modulation.
Knock-out studies in mice suggest a role of the CHRNA4 gene in anxiety. In the present study we extend this finding to humans by means of a genetic association study. In a sample of N⫽ 574 healthy White participants, the CHRNA4 rs1044396 polymorphism is related to the common variance of several conceptualizations of negative emotionality. Compared to carriers of at least one T-allele, carriers of the homozygous C/C genotype described themselves as more anxious and emotionally unstable on various psychometric personality questionnaires. The scope of the genetic effect is remarkable because other prominent genetic markers for anxiety show specificity for the diagnostic tool used. The present study is the first study that demonstrates the relevance of the CHRNA4 gene for negative emotionality in humans and sets a starting point for further investigations that could inform on the treatment of various affective psychiatric disorders.
Working memory (WM) is fractionated into systems for visuospatial and phonological information. Recently, it has been shown that the dopamine d2 receptor gene DRD2 and CHRNA4, the gene coding for the nicotinic acetylcholine receptor's alpha4 subunit, interact epistatically on visuospatial WM capacity. In the present study, we show a similar interaction on phonological WM capacity in N=137 healthy subjects genotyped for two single nucleotide polymorphisms (DRD2 rs6277 and CHRNA4 rs1044396). Given the functional independence of the two systems we hypothesize that the genetic interaction targets the central executive which is the common control process for both systems.
The adjustment of behavior to changing goals and environmental constraints requires the flexible switching between different task sets. Cognitive flexibility is an endophenotype of executive functioning and is highly heritable, as indicated by twin studies. Individual differences in global flexibility as assessed by reaction-time measurement in a task-switching paradigm were recently related to a single nucleotide polymorphism in the vicinity of the dopamine d2 receptor gene DRD2. In the present study, we assessed whether the DRD2 gene is related to backward inhibition, a control mechanism that contributes to cognitive flexibility by reducing proactive interference by no longer relevant task sets. We found that carriers of the DRD2 A1+ variant who have a lower striatal dopamine d2 receptor density than A1– carriers show a larger backward inhibition effect. This is in line with previous results demonstrating increased behavioral flexibility in carriers of this genetic variant. The discussion relates the present finding to those of previous studies assessing the neurogenetic foundations of inhibitory control.
Myotonic dystrophy types 1 and 2 are progressive multisystemic disorders with potential brain involvement. We compared 22 myotonic dystrophy type 1 and 22 myotonic dystrophy type 2 clinically and neuropsychologically well-characterized patients and a corresponding healthy control group using structural brain magnetic resonance imaging at 3 T (T(1)/T(2)/diffusion-weighted). Voxel-based morphometry and diffusion tensor imaging with tract-based spatial statistics were applied for voxel-wise analysis of cerebral grey and white matter affection (P(corrected) < 0.05). We further examined the association of structural brain changes with clinical and neuropsychological data. White matter lesions rated visually were more prevalent and severe in myotonic dystrophy type 1 compared with controls, with frontal white matter most prominently affected in both disorders, and temporal lesions restricted to myotonic dystrophy type 1. Voxel-based morphometry analyses demonstrated extensive white matter involvement in all cerebral lobes, brainstem and corpus callosum in myotonic dystrophy types 1 and 2, while grey matter decrease (cortical areas, thalamus, putamen) was restricted to myotonic dystrophy type 1. Accordingly, we found more prominent white matter affection in myotonic dystrophy type 1 than myotonic dystrophy type 2 by diffusion tensor imaging. Association fibres throughout the whole brain, limbic system fibre tracts, the callosal body and projection fibres (e.g. internal/external capsules) were affected in myotonic dystrophy types 1 and 2. Central motor pathways were exclusively impaired in myotonic dystrophy type 1. We found mild executive and attentional deficits in our patients when neuropsychological tests were corrected for manual motor dysfunctioning. Regression analyses revealed associations of white matter affection with several clinical parameters in both disease entities, but not with neuropsychological performance. We showed that depressed mood and fatigue were more prominent in patients with myotonic dystrophy type 1 with less white matter affection (early disease stages), contrary to patients with myotonic dystrophy type 2. Thus, depression in myotonic dystrophies might be a reactive adjustment disorder rather than a direct consequence of structural brain damage. Associations of white matter affection with age/disease duration as well as patterns of cerebral water diffusion parameters pointed towards an ongoing process of myelin destruction and/or axonal loss in our cross-sectional study design. Our data suggest that both myotonic dystrophy types 1 and 2 are serious white matter diseases with prominent callosal body and limbic system affection. White matter changes dominated the extent of grey matter changes, which might argue against Wallerian degeneration as the major cause of white matter affection in myotonic dystrophies.
BACKGROUND: Pharmacological studies indicate a functional interaction between the serotonergic and oxytocinergic system. METHODS: This study tested for an interaction of the prominent serotonin transporter polymorphism (SLC6A4) and an oxytocin receptor gene variation on individual differences in negative emotionality in healthy Caucasians (n = 750). RESULTS: Participants carrying both the homozygous LL-variant of the serotonin transporter polymorphism and the TT variant of the single nucleotide polymorphism rs2268498 on the oxytocin receptor gene showed lowest scores on the personality dimensions Fear and Sadness of the Affective Neuroscience Personality Scales, as well as on an underlying factor Negative Emotionality. CONCLUSIONS: The observed interaction effect provides converging evidence from human molecular genetics that serotonergic and oxytocinergic neurotransmission are entwined and play a crucial role for human personality with implications for affective disorders.
The present study investigated the influence on Internet addiction of numerous variables ranging from personality to psychological and physical well-being, in a large and highly ecologically valid sample of mainly male adolescent online computer gamers (first-person-shooter video gamers) in Germany. Low Self-Directedness could be linked to a high Internet Addiction Test score in the present study, and the data yielded a continuum model indicating that low Self-Directedness is highly correlated with Internet Addiction Score, not only in students but also in first-person-shooter video gamers.
The present fMRI study investigates individual differences in human brain activity during listening to one's favorite and one's most unlikeable song. In 33 participants, we found that the contrast of listening to pleasant versus unpleasant music revealed a robust activation of the ventral striatum, the caudate nucleus and the insula across a group of participants. Moreover, we could demonstrate that activity within the ventral striatum was modulated by the subscale 'self-forgetfulness' of the character dimension 'self-transcendence'.
Panic disorder (PD) is a serious and common psychiatric condition1 characterized mainly by recurrent episodes of intense, uncontrollable fear known as panic attacks.2 The underlying causal mechanism for PD is unknown;3 however, the discovery that drugs with clinical effectiveness against PD preferentially alter rodent flight behaviour suggests that PD reflects alterations in the brain systems that govern flight.4 An association between PD and flight in humans is supported anecdotally by the tendency for PD sufferers to feel a strong urge to flee from the location where a panic attack occurs.2 Here we provide the first human empirical evidence for a PD–flight link, showing that flight behaviour is significantly more intense in carriers of a candidate genetic risk factor for PD than in non-carriers.
The following article describes a study of the neural correlates of compulsive buying. Twenty-six non-compulsive (“normal”) and 23 compulsive buyers were measured using functional magnetic resonance imaging while performing purchasing decisions. The compulsive buyers were selected based on strict criteria, such that they were all undergoing psychotherapeutic treatment due to their buying behaviour. The results show evidence of significant differences between non-compulsive and compulsive buyers regarding brain activity in regions known to be involved in decision making. The findings give a deeper insight into the nature of compulsive buying and are relevant to consumer policy.
Acoustic radiation contrast in magnetic resonance images is an approach to visualize the changes in ultrasonic loss and viscoelastic changes of the sample with the resolution of a magnetic resonance imaging (MRI) system. By irradiating ultrasound (US) into a tissue-mimicking sample, a displacement along the US beam path caused by the acoustic radiation force is obtained. This displacement varies with the US intensity, the duration of irradiation, the US attenuation and the viscoelastic properties of the sample. US pulses of 2.5 MHz with a duration of 20 ms and an intensity of <17 W/cm(2) are used. An MRI sequence was programmed to produce images in which the magnitude of the displacement is visualized by gray value changes. In addition, a finite element simulation of the measurements was performed to demonstrate the feasibility of the method. Through examination of the measurements and the simulations, information about viscoelastic changes was achieved. In this work, measurements on different breast phantoms are presented.
Although the field of psychology is undergoing an immense shift toward the use of functional magnetic resonance imaging (fMRI), the application of this methodology to consumer research is rela- tively new. To assist consumer researchers in understanding fMRI, this paper elaborates on the findings of prior fMRI research related to consumer behavior and highlights the features that make fMRI an attractive method for consumer and marketing research. The authors discuss advantages and limitations and illustrate the proposed procedures with an applied study, which investigates loss aversion when buying and selling a common product. Results reveal a significantly stronger activation in the amygdala while consumers estimate selling prices versus buying prices, suggesting that loss aversion is associated with the processing of negative emotion.
Findings from twin studies yield heritability estimates of 0.50 for prosocial behaviours like empathy, cooperativeness and altruism. First molecular genetic studies underline the influence of polymorphisms located on genes coding for the receptors of the neuropeptides, oxytocin and vasopressin. However, the proportion of variance explained by these gene loci is rather low indicating that additional genetic variants must be involved. Pharmacological studies show that the dopaminergic system interacts with oxytocin and vasopressin. The present experimental study tests a dopaminergic candidate polymorphism for altruistic behaviour, the functional COMT Val158Met SNP. N = 101 healthy Caucasian subjects participated in the study. Altruism was assessed by the amount of money donated to a poor child in a developing country, after having earned money by participating in two straining computer experiments. Construct validity of the experimental data was given: the highest correlation between the amount of donations and personality was observed for cooperativeness (r = 0.32, P ≤ 0.001). Carriers of at least one Val allele donated about twice as much money as compared with those participants without a Val allele (P = 0.01). Cooperativeness and the Val allele of COMT additively explained 14.6% of the variance in donation behaviour. Results indicate that the Val allele representing strong catabolism of dopamine is related to altruism.
This paper analyzes whether there exists a causal relationship between parental employment and children’s educational attainment. We address potential endogeneity problems due to (i) selection of parents in the labor market by estimating a model on sibling differences and (ii) reverse causality by focusing on parents’ employment when children are aged 0–3. We use data from the German Socioeconomic Panel that provide information on household income, parental employment, and time spent with child care. Our approach disentangles income and time effects of parental employment. Overall, we find little support that parental employment affects children’s educational attainment. Controlling for household income, we can rule out that having a mother who works one hour more per week lowers the probability of high secondary track attendance by more than 0.1%.
Neuroimaging studies on attention-deficit/hyperactivity disorder (ADHD) suggest dysfunctional reward processing, with hypo-responsiveness during reward anticipation in the reward system including the nucleus accumbens (NAcc). In this study, we investigated the association between ADHD related behaviors and the reward system using functional magnetic resonance imaging in a non-clinical sample. Participants were 31 healthy, female undergraduate students with varying levels of self-reported ADHD related behaviors measured by the adult ADHD self-report scale. The anticipation of different types of reward was investigated: monetary reward, punishment avoidance, and verbal feedback. All three reward anticipation conditions were found to be associated with increased brain activation in the reward system, with the highest activation in the monetary reward anticipation condition, followed by the punishment avoidance anticipation condition, and the lowest activation in the verbal feedback anticipation condition. Most interestingly, in all three conditions, NAcc activation was negatively correlated with ADHD related behaviors. In conclusion, our results from a non-clinical sample are in accordance with reported deficits in the reward system in ADHD patients: the higher the number and severity of ADHD related behaviors, the lower the neural responses in the dopaminergic driven reward anticipation task. Thus, our data support current aetiological models of ADHD which assume that deficits in the reward system might be responsible for many of the ADHD related behaviors.
It is still debated how altruistic punishment as one form of strong reciprocity has established during evolution and which motives may underlie such behavior. Recent neuroscientific evidence on the activation of brain reward regions during altruistic punishment in two-person one-shot exchange games suggests satisfaction through the punishment of norm violations as one underlying motive. In order to address this issue in more detail, we used fMRI during a one-shot economic exchange game that warrants strong reciprocity by introducing a third party punishment condition wherein revenge is unlikely to play a role. We report here that indeed, reward regions such as the nucleus accumbens showed punishment-related activation. Moreover, we provide preliminary evidence that genetic variation of dopamine turnover impacts similarly on punishment-related nucleus accumbens activation during both first person and third party punishment. The overall pattern of results suggests a common cognitive-affective-motivational network as the driving force for altruistic punishment, with only quantitative differences between first person and third party perspectives.
Understanding causal relationships, or effective connectivity, between parts of the brain is of utmost importance because a large part of the brain's activity is thought to be internally generated and, hence, quantifying stimulus response relationships alone does not fully describe brain dynamics. Past efforts to determine effective connectivity mostly relied on model based approaches such as Granger causality or dynamic causal modeling. Transfer entropy (TE) is an alternative measure of effective connectivity based on information theory. TE does not require a model of the interaction and is inherently non-linear. We investigated the applicability of TE as a metric in a test for effective connectivity to electrophysiological data based on simulations and magnetoencephalography (MEG) recordings in a simple motor task. In particular, we demonstrate that TE improved the detectability of effective connectivity for non-linear interactions, and for sensor level MEG signals where linear methods are hampered by signal-cross-talk due to volume conduction.
Focal cortical dysplasias type II (FCD II) are highly epileptogenic lesions frequently causing pharmacoresistant epilepsy. Detection of these lesions on MRI is still challenging as FCDs may be very subtle in appearance and might escape conventional visual analysis. Morphometric MRI analysis is a voxel-based post-processing method based on algorithms of the statistical parametric mapping software (SPM5). It creates three dimensional feature maps highlighting brain areas with blurred grey-white matter junction and abnormal gyration, and thereby may help to detect FCD. In this study, we evaluated the potential diagnostic value of morphometric analysis as implemented in a morphometric analysis programme, compared with conventional visual analysis by an experienced neuroradiologist in 91 patients with histologically proven FCD II operated on at the University Hospital of Bonn between 2000 and 2010 (FCD IIa, n = 17; IIb, n = 74). All preoperative MRI scans were evaluated independently (i) based on conventional visual analysis by an experienced neuroradiologist and (ii) using morphometric analysis. Both evaluators had the same clinical information (electroencephalography and semiology), but were blinded to each other's results. The detection rate of FCD using morphometric analysis was superior to conventional visual analysis in the FCD IIa subgroup (82% versus 65%), while no difference was found in the FCD IIb subgroup (92% versus 91%). However, the combination of conventional visual analysis and morphometric analysis provided complementary information and detected 89 out of all 91 FCDs (98%). The combination was significantly superior to conventional visual analysis alone in both subgroups resulting in a higher diagnostic sensitivity (94% versus 65%, P = 0.031 for FCD IIa; 99% versus 91%, P = 0.016 for FCD IIb). In conclusion, the additional application of morphometric MRI analysis increases the diagnostic sensitivity for FCD II in comparison with conventional visual analysis alone. Since detection of FCDs on MRI during the presurgical evaluation markedly improves the chance of becoming seizure free postoperatively, we apply morphometric analysis in all patients who are MRI-negative after conventional visual analysis at our centre.
OBJECTIVE: To test the hypothesis that the interaction between the brain-derived neurotrophic factor (BDNF) and dopamine receptor D(2) (DRD2)/ANKK1 gene contributes to individual differences in alexithymia. The personality construct of alexithymia refers to difficulties in emotional self-regulation and contributes as a risk factor to several mental disorders. Alexithymic individuals show an impoverished conscious experience of emotions but an intact autonomic emotional response. Persons with high alexithymia scores reportedly show a reduced activation of the anterior cingulate cortex (ACC) during the processing of emotional stimuli. An interaction between two polymorphisms on the BDNF and DRD2/ANKK1 gene has been recently associated with reduced gray matter volume in the ACC and higher trait anxiety. METHODS: We conducted a genetic association study. A total of 664 healthy participants completed the Toronto Alexithymia Scale questionnaire and were genotyped for the BDNF Val66Met (rs6265) and the DRD2/ANKK1 Taq IA (rs1800497) polymorphisms. RESULTS: Carriers of at least one BDNF 66Met and one DRD2/ANKK1 A1 allele showed the highest scores in the total Toronto Alexithymia Scale and in the subscale "Difficulties Identifying Feelings." CONCLUSION: In line with recent studies investigating the role of BDNF Val66Met and DRD2/ANKK1 Taq IA polymorphisms on anxiety and gray matter volume in the ACC, our findings provide the first evidence for a genetic contribution to alexithymia.
AIMS: To investigate the effects of actual and expected alcohol intake on the detection and interpretation of the basic emotions happiness and anger in facial expressions. METHODS: n = 102 healthy participants performed a dynamic emotion recognition task before and after receiving a drink which contained either a moderate alcohol dose or no alcohol in a double-blind design. RESULTS: The actual alcohol intake had no effect on detecting and interpreting facial expressions. However, subjects who expected to drink alcohol judged facial expressions significantly more often as happy. No effects were observable for the recognition of anger in facial expressions. CONCLUSION: Our results corroborate recent studies that found that the belief of consuming alcohol does not increase anger recognition or aggressive behavior but decreases aggression and social stress.
The analysis of cortical and subcortical networks requires the identification of their nodes, and of the topology and dynamics of their interactions. Exploratory tools for the identification of nodes are available, e.g. magnetoencephalography (MEG) in combination with beamformer source analysis. Competing network topologies and interaction models can be investigated using dynamic causal modelling. However, we lack a method for the exploratory investigation of network topologies to choose from the very large number of possible network graphs. Ideally, this method should not require a pre-specified model of the interaction. Transfer entropy – an information theoretic implementation of Wiener-type causality – is a method for the investigation of causal interactions (or information flow) that is independent of a pre-specified interaction model. We analysed MEG data from an auditory short-term memory experiment to assess whether the reconfiguration of networks implied in this task can be detected using transfer entropy. Transfer entropy analysis of MEG source-level signals detected changes in the network between the different task types. These changes prominently involved the left temporal pole and cerebellum – structures that have previously been implied in auditory short-term or working memory. Thus, the analysis of information flow with transfer entropy at the source-level may be used to derive hypotheses for further model-based testing.
2010
We study how different payment modes influence the effectiveness of gift exchange as a contract enforcement device. In particular, we analyze how horizontal fairness concerns affect performance and efficiency in an environment characterized by contractual incompleteness. In our experiment, one principal is matched with two agents. The principal pays equal wages in one treatment and can set individual wages in the other. We find that the use of equal wages elicits substantially lower efforts. This is not caused by monetary incentives per se because under both wage schemes it is profit-maximizing for agents to exert high efforts. The treatment difference instead seems to be driven by the fact that the norm of equity is violated far more frequently in the equal wage treatment. After having suffered from violations of the equity principle, agents withdraw effort. These findings hold even after controlling for the role of intentions, as we show in a third treatment. Our results suggest that adherence to the norm of equity is a necessary prerequisite for successful establishment of gift-exchange relations.
We analyse worker self-selection, with a special focus on teachers, to explore whether worker composition is generally endogenous. We analyse laboratory experimental data to provide causal evidence on particular sorting patterns. Our field data analysis focuses specifically on selection patterns of teachers. We find that teachers are more risk averse than employees in other professions, indicating that relatively risk averse individuals sort into teaching occupations under the current system. Using survey measures on trust and reciprocity we find that teachers trust more and are less negatively reciprocal than other employees, and establish differences in personality based on the Big Five concept.
This paper investigates whether there is a link between cognitive ability, risk aversion, and impatience, using a representative sample of roughly 1,000 German adults. Subjects participate in choice experiments with monetary incentives measuring risk aversion, and impatience over an annual horizon, and conduct two different, widely used, tests of cognitive ability. We find that lower cognitive ability is associated with greater risk aversion, and more pronounced impatience. These relationships are significant, and robust to controlling for personal characteristics, education, income, and measures of credit constraints. We perform a series of additional robustness checks, which help rule out other possible confounds.
Deeper semantic processing of words leads to enhanced memory encoding (depth of processing effect). The left inferior prefrontal cortex (LIPC) and the left hippocampus are known to be involved in this effect. We tested the hypothesis that different semantic encoding processes contribute qualitatively differently to memory encoding. In a memory experiment using functional magnetic resonance imaging, we compared three different encoding tasks: a nonsemantic alphabetical, an animacy decision, and a size comparison tasks. Recognition memory was tested subsequently. We hypothesized that the size comparison task would activate brain areas involved in the processing of object features and that this would be associated with successful memory encoding. Results showed that the size comparison task led to significantly better memory encoding than the two other tasks. As with the animacy decision task, it led to stronger activation of the LIPC and left hippocampus than the nonsemantic task. Both regions also had stronger activations for later remembered than for nonremembered words. The size comparison task additionally led to stronger activation in the left anterior fusiform gyrus, which was also associated with successful memory encoding. We conclude that different types of semantic processing affect memory encoding based on distinguishable brain processes.
NeuroCogFX is a short yet comprehensive computer-based neuropsychological battery of tests developed to investigate neurological patients for cognitive dysfunction after potentially neurotoxic therapy. NeuroCogFX had been standardized in a group of 242 healthy controls (Fliessbach et al., Fortschr Neurol Psychiatr 74:643-650, 2006). The present study was conducted to assess the practicability, reliability, and validity of NeuroCogFX in brain tumor patients without active disease after tumor-directed therapy. To evaluate its validity, neuropsychological testing with NeuroCogFX was completed parallel to a battery of established neuropsychological tests in 54 patients with different types of brain tumors and without active disease for at least 6 months. Retest reliability was assessed in a different sample of 49 patients with gliomas. Results showed good practicability with a median test duration of 28 min (range 16-51 min). Most subtests showed medium-sized retest reliability in healthy controls and tumor patients, with the exception of the 2-back test and reaction time measures in tumor patients. Convergent validity was confirmed for the domains psychomotor speed, verbal memory, and verbal short-term memory. NeuroCogFX enables serial scientific neuropsychological assessment of brain tumor patients. It can be carried out within a short period of time by non-academic personnel and is therefore applicable to large cohorts, e.g., within clinical trials.
Reward processing is a central component of learning and decision making. Functional magnetic resonance imaging (fMRI) has contributed essentially to our understanding of reward processing in humans. The strength of reward-related brain responses might prove as a valuable marker for, or correlate of, individual preferences or personality traits. An essential prerequisite for this is a sufficient reliability of individual measures of reward-related brain signals. We therefore determined test-retest reliabilities of BOLD responses to reward prediction, reward receipt and reward prediction errors in the ventral striatum and the orbitofrontal cortex in 25 subjects undergoing three different simple reward paradigms (retest interval 7-13 days). Although on a group level the paradigms consistently led to significant activations of the relevant brain areas in two sessions, across-subject retest reliabilities were only poor to fair (with intraclass correlation coefficients (ICCs) of -0.15 to 0.44). ICCs for motor activations were considerably higher (ICCs 0.32 to 0.73). Our results reveal the methodological difficulties behind across-subject correlations in fMRI research on reward processing. These results demonstrate the need for studies that address methods to optimize the retest reliability of fMRI.
The importance of fair and equal treatment of workers is at the heart of the debate in organizational management. In this regard, we study how reward schemes and production technologies affect effort provision in teams. Our experimental results demonstrate that unequal rewards can potentially increase productivity by facilitating coordination and that the effect strongly interacts with the exact shape of the production function. Taken together, our data highlight the relevance of the production function for organization construction and suggest that equal treatment of equals is neither a necessary nor a sufficient prerequisite for eliciting high performance in teams.
Hyposmia is one of the early signs in idiopathic Parkinson's disease (PD). Olfactory stimuli were applied during fMRI scanning to show disease-related modulation of central nervous system structures and to advance our understanding of olfactory dysfunction in PD patients. All participants received either unpleasant stimuli that smelled like rotten eggs or pleasant ones that smelled like roses. Using a block design at a 1.5 T scanner we investigated a total of 8 PD patients (mean age 60 ± 10.9 years) and 13 age matched controls (mean age 58 ± 9.6 years). PD duration ranged from 1 to 9 years (mean 6.63 years); patients had an average "Unified Parkinson's Disease Rating Scale III" score of 23.25 (range, 6-46). Olfactory function was established using the "Sniffin' Sticks" test battery. Patients tended to rate the stimuli presented during fMRI scans as less intense, but also as more pleasant than controls. fMRI results revealed differences between PD patients and controls which depended on the type of stimulation. While both pleasant and unpleasant stimulation was associated with lower activation in the amygdalo-hippocampal complex in patients compared to controls, increased activity in response to pleasant stimuli was observed in the striatum and the left inferior frontal gyrus. In contrast, unpleasant stimulation led to hypoactivation of the ventral striatum in patients (but not in controls) and did not enhance left inferior frontal activity. These results may partly reflect differences between PD patients and healthy controls in the processing of primary dimensions of odors, intensity, and valence.
It has long been hypothesized that individuals' migration propensities depend on their risk attitudes, but the empirical evidence has been limited and indirect. We use newly available data from the German Socio-Economic Panel to measure directly the relationship between migration and risk attitudes. We find that individuals who are more willing to take risks are more likely to migrate. Our estimates are substantial compared to unconditional migration probabilities, as well the effects of conventional determinants of migration, and are robust to controlling for a variety of demographic characteristics. We find no evidence that our results are the result of reverse causality.
OBJECTIVE: To evaluate long-term progression-free survival and overall survival, quality of life, and cognitive function in primary central nervous system lymphoma after systemic and intraventricular chemotherapy without radiotherapy. METHODS: A long-term follow-up was conducted on surviving primary central nervous system lymphoma patients having been enrolled in a pilot/phase II trial between September 1995 and December 2001. Initially, 65 patients (median age, 62 years) had been treated with systemic and intraventricular chemotherapy without radiotherapy. All living patients were contacted, and a neurological examination, comprehensive neuropsychological testing, quality-of-life assessment, and imaging were performed. RESULTS: Twenty-one of all 65 patients (32 %) and 17 of 30 patients 60 years or younger (57%), respectively, were still alive at median follow-up of 100 months (range, 77-149 months). Nineteen of 21 patients completed all investigations; 1 was lost to follow-up. In three patients, an exclusively extraneural relapse of a high-grade non-Hodgkin's lymphoma was diagnosed after 9, 31, and 40 months, respectively. All of them experienced complete remission to high dose. Neither late neurotoxicity nor compromise of quality of life was found in any of the patients examined. INTERPRETATION: Primary polychemotherapy based on high-dose methotrexate (MTX) and cytarabine (Ara-C) is highly efficient in treatment of primary central nervous system lymphoma. About half of patients 60 years or younger can obviously be cured with this regimen without long-term neurotoxic sequelae or quality-of-life compromise.
Everyday we choose between a variety of different food items trying to reach a decision that fits best our needs. These decisions are highly dependent on the context in which the alternatives are presented (e.g. labeling). We investigate the influence of cognition on food evaluation, using an fMRI experiment in which subjects saw and bid on different foods labeled with (or without) a widely known German emblem for organically produced food. Increased activity in the ventral striatum was found for foods labeled "organic" in comparison to conventionally labeled food. Between-subject differences in activity were related to actual everyday consumption behavior of organic food.
Working memory capacity is extremely limited and individual differences are heritable to a considerable extent. In the search for a better understanding of the exact genetic underpinnings of working memory, most research has focused on functional gene variants involved in the metabolism of the neurotransmitter dopamine. Recently, there has been investigation of genes related to other neurotransmitter systems such as acetylcholine. The potential relevance of a polymorphism located in the gene coding for the alpha4 subunit of the nicotinic acetylcholine receptor (rs#1044396) has been discussed with respect to working memory, but empirical investigations have provided mixed results. However, pharmacological studies in both rodents and humans have shown that the effect of nicotinic agonists on cognitive functions is mediated by dopamine. We therefore hypothesized that such an interaction can be found on a molecular genetic level as well. In order to test this hypothesis, we genotyped 101 healthy subjects for rs#1044396 and three functional polymorphisms on the dopamine d2 receptor gene (rs#1800497, rs#6277, rs#2283265). These subjects performed a visuospatial working memory task in which memory load was systematically varied. We found a significant interaction between rs#1044396 and a haplotype block covering all three dopaminergic polymorphisms on working memory capacity. This effect only became apparent on higher levels of working memory load. This is the first evidence from a molecular genetic perspective that these two neurotransmitter systems interact on cognitive functioning. The results are discussed with regard to their implication for working memory theories and their clinical relevance for treatment of substance abuse and schizophrenia.
Purpose: Mammography is a widely used tool for the screening of breast cancer, and calcifications are a common finding in most mammograms. The location, size, number, morphology, and distri- bution of calcifications are an important information to differentiate a benign lesion from probably malignant pathologies. Calcifications are not detectable with a standard dynamic contrast enhanced breast MRI. The authors present a novel method for the detection and imaging of calcifications in breast tissue without ionizing radiation or contrast agents. Methods: Measurements of localized tissue displacement in phantoms due to applied acoustic radiation force were performed. This displacement was imaged with a displacement sensitive spin- echo MRI sequence. Pieces of eggshell that represent calcifications were embedded in tissue- mimicking agarose phantoms. The sizes of the calcifications were 0.8⫻0.8⫻0.4, 1.5⫻1.5⫻0.4, and 2⫻3⫻0.4 mm3. The calcifications were scanned with ultrasound 共U.S.兲 at 2.5 MHz and intensities up to Ispta=7.18 W/cm2. The U.S. beam was moved inside the phantom by a computer- controlled three-dimensional hydraulic positioning system. The U.S. beam was scanned over the two smaller calcifications with the displacement sensitivity of the MRI sequence parallel to the U.S. beam path. Grayscale coded maps of the displacement scans are presented. For the 0.8⫻0.8 ⫻0.4 mm3 calcification, the U.S. intensities were varied. Finite element simulations were per- formed to verify if the experiments complied with theory. Results: The authors found that the displacement caused by the U.S. is increased at the position of the calcification. The area of increased displacement is at least twice as large as the calcification itself. The simulations show this increase in displacement and area at the position of the calcifica- tion. When changing the displacement sensitivity direction to perpendicular to the U.S. beam, a crossed black and white four-leaf clover is visible at the position of the calcification. Conclusions: The U.S. is scattered and reflected by the calcifications. This leads to the increased displacement which is transmitted to the surrounding material because of the elastic coupling between the calcification and the agarose material. Due to the high differences in acoustic impped- ance and elastic properties between the surrounding tissue and the calcification, even the detection of pieces smaller than the resolution of the MRI scanner is possible. The acoustic radiation force contrast in MR phase-difference images offers a positive signal for calcifications from a smooth background in phantoms. This method offers a possibility of differentiating qualitatively and quan- titatively hard calcifications from stiffer inclusions such as tumors.
Mounting evidence shows that the brain derived neurotrophic factor (BDNF) plays a crucial role in depression and anxiety. The discovery of a functional variant of the BDNF gene –the BDNF Val66Met polymorphism – led to new insights into the molecular genetic mechanisms underlying these emotional disorders. Although there is evidence from animal research that the homozygous BDNF 66Met variant is associated with anxiety-like behaviour, findings from personality research using self-report-measures as indicators of trait anxiety are heterogenous. Recent seminal findings from a study using a knock-in mouse design suggest that this Met66Met group is of particular interest for the investigation of the molecular genetic mechanisms of anxiety and anxiety-related personality traits in humans. In a sample of 610 Caucasian participants, subjects homozygous for the 66Met allele scored significantly higher than Val66 allele carriers on anxiety-related facets of the construct 'harm avoidance' (i.e., 'anticipatory worry' and 'fear of uncertainty') of the Temperament and Character Inventory. This finding adds to a small plurality of studies that associates the 66Met allele, rather than the Val66 allele, with higher anxiety scores. Importantly, the present results furthermore suggest that it is the occurrence of not one but two 66Met alleles that is associated with high trait anxiety.
The classification of internet addiction as a distinct diagnosis in the upcoming DSM-V is currently under debate. Nevertheless, before this issue is resolved, there are important related questions in the field of internet addiction that are in need of an answer, e.g. which personality dimensions may predispose towards problematic internet use. One such factor seems to be neuroticism. However, a sole factor like neuroticism alone is not very useful with respect to generating implications for behavior therapy and treatment of afflicted patients, because it includes too many facets of negative personality traits ranging from shyness to anxiety. Therefore, in this study we aimed to measure the grade of problematic internet use with the internet addiction test (IAT); moreover, we measured personality with Eysenck’s Personality Questionnaire (EPQ-R) and with the Temperament and Character Inventory (TCI). In addition to the EPQ- R, the TCI provides further information with respect to which facets of personality are associated with problematic internet use. In N = 201 participants, we found that self-directedness is a better predictor than neuroticism for problematic internet use. Moreover, the time spent online in leisure activities was a significant predictor for a high IAT score. Implications for behavior therapy are discussed.
Mounting evidence from animal studies show that the mesolimbic dopaminergic pathways are modulated by the brain-derived neurotrophic factor (BDNF). This study investigates in N=768 healthy Caucasian participants the influence of two prominent functional single-nucleotide polymorphisms (SNPs) on the BDNF gene (BDNF Val66Met SNP) and the ankyrin repeat and kinase domain containing 1 (ANKK1) gene (DRD2 Taq Ia/ANKK1 SNP) on the personality traits of Novelty Seeking and Harm Avoidance, which are mediated, in part, through dopaminergic mesolimbic circuitry. Carriers of the 66Met+/A1+ variant scored lowest on Novelty Seeking and highest on Harm Avoidance, compared to all other genotype groups. These participants are characterized by a relatively low D(2) receptor density in the striatum and an impaired activity-dependent secretion of BDNF. This is one of the first genetic association studies to show a modulatory role for BDNF genetic variation on genetically mediated differences in the mesolimbic dopaminergic system in the context of human personality.
The brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and involved in nerve growth and survival. It has also become a major research focus in the investigation of both cognitive and affective processes in the human brain in the last years. Especially, a single nucleotide polymorphism on the BDNF gene called BDNF Val66Met gained a lot of attention, because of its effect on activity-dependent BDNF secretion and its link to negative emotionality and impaired memory processes. A well-replicated finding from genetic structural imaging showed that carriers of the less frequent 66Met allele show diminished gray matter volume in several areas of the temporal lobe. New imaging techniques like diffusion tensor imaging now allow investigating the influence of BDNF Val66Met on white matter integrity. We applied tract-based spatial statistics in a brain image dataset including n = 99 healthy participants. No significant differences between the 66Met and homozygous 66Val carriers were observed when correcting for multiple comparisons. In summary, the BDNF Val66Met polymorphism seems not to play a substantial role with respect to the modulation of the white matter integrity in healthy subjects. Although not in the focus of this study, we also investigated the influence of Eysenck's Personality Questionnaire on the white matter tracts. No significant results could be observed.
Recent evidence suggests that mesolimbic dopaminergic pathways are regulated by the brain derived neurotrophic factor (BDNF). The present study shows that the prominent single nucleotide polymorphisms (SNPs) BDNF Val66Met and DRD2 Taq Ia/ANKK1 exert an epistasis effect on the anterior cingulate cortex (ACC) in 161 healthy Caucasian participants. Carriers with at least one 66Met allele (Val66Met and Met66Met) of the BDNF SNP and one A1 allele (A1/A1 and A1/A2) of the DRD2 SNP are associated with the lowest gray matter volume of the ACC in the current sample. As the smaller gray matter volume of the ACC has been associated with addiction before, this study yields evidence that especially carriers of both allele variants that have been associated with addiction and other psychopathological disorders before might have an increased risk to develop psychiatric symptoms under adverse environmental conditions.
Laterality is a characteristic principle of the organization of the brain systems for language, and reduced hemispheric asymmetry has been considered a risk factor for schizophrenia. Here we sought support for the risk factor hypothesis by investigating whether reduced asymmetry of temporal lobe structure and function is also present in unaffected relatives. Sixteen schizophrenia patients, 16 age-matched first-degree relatives, and 15 healthy controls underwent high-resolution three-dimensional anatomical imaging and functional magnetic resonance imaging during auditory stimulation. Both the overall auditory cortex and planum temporale volumes and the lateralization to the left hemisphere were markedly reduced in patients. The decrease of lateralization correlated with increased severity of symptoms. In addition, both the overall functional activation in response to auditory stimulation and its asymmetry were reduced in the patients. Relatives had intermediate values between patients and controls on both structural and functional measures. This study provides added support for the idea that reduced hemispheric asymmetry is a biological risk factor for schizophrenia.
Abstract Objectives—Individuals with anorexia nervosa (AN) and bulimia nervosa (BN) tend to have disordered thinking and eating behaviours in regards to fat containing foods. This is the first study to investigate neuronal pathways that may contribute to altered fat consumption in eating disordered patients. Methods—We used functional magnetic resonance imaging (fMRI) to compare responses to a high-fat cream stimulus, water, and a non-caloric viscous stimulus (CMC) to control for response to viscosity in individuals recovered from AN (N = 15), BN (N = 14) and a healthy control sample (CW, N = 18). Results—An interaction analysis (ANOVAR) comparing the three groups (AN, BN, CW) and the three conditions (cream, CMC, water) revealed significant differences in the left anterior ventral striatum (AVS). A post hoc analysis displayed a higher magnitude of response for the contrast cream/water in BN compared to AN or CW and for the contrast CMC/water in BN compared to AN.
In four experiments, this research sheds light on aesthetic experiences by rigorously investigating behavioral, neural, and psychological properties of package design. We find that aesthetic packages significantly increase the reaction time of consumers' choice responses; that they are chosen over products with well-known brands in standardized packages, despite higher prices; and that they result in increased activation in the nucleus accumbens and the ventromedial prefrontal cortex, according to functional magnetic resonance imaging (fMRI). The results suggest that reward value plays an important role in aesthetic product experiences. Further, a closer look at psychometric and neuroimaging data finds that a paper-and-pencil measure of affective product involvement correlates with aesthetic product experiences in the brain. Implications for future aesthetics research, package designers, and product managers are discussed.
This article reflects on the discussions of the fifteen participants (co-authors) of a retreat on the “Foundations of NeuroIS” that took place in Gmunden (Austria) in September 2009. In particular, this article offers initial answers to a set of research questions which are important for the foundations of NeuroIS, an emerging subfield within the IS discipline. The key questions discussed during the retreat that are addressed in this article are: (1) What is NeuroIS, and how does it relate to sister disciplines, such as neuroscience, neuroeconomics, and neuromarketing? (2) Which neuroscience tools are relevant for IS research? (3) What can IS researchers learn from the neuroscience literature, and what do we already know about brain activity? (4) What are possible IS research topics that can be examined with neuroscience tools, and what are some promising research areas for NeuroIS? (5) How can NeuroIS be established as a new subfield in the IS literature, and what are the current challenges for NeuroIS? The article concludes by offering the participants’ outlook on the future of NeuroIS.
We implement the Rawlsian veil of ignorance in the laboratory. Our design allows analyzing the effects of risk and social preferences behind the veil of ignorance. Behind the veil of ignorance subjects choose more equal distributions than in front of the veil, but only a minority acts according to maximin preferences. Many subjects prefer more equal allocations not only for insurance purposes but also due to impartial social preferences for equality. Our results imply that behind the veil of ignorance maximin preferences are compatible with any degree of risk aversion if impartial social preferences for equality are sufficiently strong.
While all-pay auctions are well researched experimentally, we do not have much laboratory evidence on wars of attrition. This paper tries to fill this gap. Technically, there are only a few differences between wars of attrition and all-pay auctions. Behaviorally, however, we find striking differences: As many studies, our experiment finds overbidding in all-pay auctions. In contrast, in wars of attrition we observe systematic underbidding. We study bids and expenditures in different experimental frames and matching procedures and tie in with the literature on stepwise linear bidding functions.
Crime has to be punished, but does punishment reduce crime? We conduct a neutrally framed laboratory experiment to test the deterrence hypothesis, namely that crime (weakly) decreases in deterrent incentives, that is, severity and probability of punishment. In our experiment, subjects can steal from another subject. Deterrent incentives vary across and within sessions. Our across-subjects analysis rejects the deterrence hypothesis: except for high levels of incentives, subjects steal on average more the stronger the incentives. We observe two types of subjects: selfish subjects who act according to the deterrence hypothesis and fair-minded subjects for whom small incentives backfire.
Various surgical brain ablation procedures for the treatment of refractory depression were developed in the twentieth century. Most notably, key target sites were (i) the anterior cingulum, (ii) the anterior limb of the internal capsule, and (iii) the subcaudate white matter, which were regarded as effective targets. Long-term symptom remissions were better following lesions of the anterior internal capsule and subcaudate white matter than of the cingulum. It is possible that the observed clinical improvements of these various surgical procedures may reflect shared influences on presently unspecified brain affect-regulating networks. Such possibilities can now be analyzed using modern brain connectivity procedures such as diffusion tensor imaging (DTI) tractography. We determined whether the shared connectivities of the above lesion sites in healthy volunteers might explain the therapeutic effects of the various surgical approaches. Accordingly, modestly sized historical lesions, especially of the anatomical overlap areas, were 'implanted' in brain-MRI scans of 53 healthy subjects. These were entered as seed regions for probabilistic DTI connectivity reconstructions. We analyzed for the shared connectivities of bilateral anterior capsulotomy, anterior cingulotomy, subcaudate tractotomy, and stereotactic limbic leucotomy (a combination of the last two lesion sites). Shared connectivities between the four surgical approaches mapped onto the most mediobasal aspects of bilateral frontal lobe fibers, including the forceps minor and the anterior thalamic radiations that contacted subgenual cingulate regions. Anatomically, convergence of these shared connectivities may derive from the superolateral branch of the medial forebrain bundle (MFB), a structure that connects these frontal areas to the origin of the mesolimbic dopaminergic 'reward' system in the midbrain ventral tegmental area. Thus, all four surgical anti-depressant approaches may be promoting positive affect by converging influences onto the MFB.
Collecting biomarkers as part of general purpose surveys offers scientists – and social scientists in particular – the ability to study biosocial phenomena, e.g. the relation between genes and human behavior. We explore the feasibility of collecting buccal cells for genetic analyses with normal interviewers as part of a pretest for the German Socio-economic Panel Study (SOEP) using a probability sample. We introduce a new non-invasive technique for collecting cell material for genetic analyses and test its quality. We found no technical difficulties in collecting the genetic material and almost all samples collected could be analyzed. However, one third of interviewers reported it was hard to convince panel members to participate. The “biomarker wave” showed no reduction in response rate compared to the previous wave that included no biomarkers and the sample exhibited very little selectivity. We conclude that collecting cell material for genetic analyses with normal interviewers is feasible with no apparent same-wave attrition, though so far we cannot rule out attrition in subsequent waves.
Recent advances in neuroimaging allow mental states to be inferred from non-invasive data. In a new study, memories of complex events were successfully decoded solely from imaged activation in a memory-related brain structure.
Recent studies suggest an association of dopamine D2 receptor (DRD2) availability with flexibility in reward-based learning. We extend these results by demonstrating an association of genetically based differences in DRD2 density with the ability to intentionally switch between nonrewarded tasks: noncarriers of the A1 allele of the DRD2/ANKK1-TaqIa polymorphism, associated with higher DRD2 density, show increased task-switching costs, increased prefrontal switching activity in the inferior frontal junction area, and increased functional connectivity in dorsal frontostriatal circuits, relative to A1 allele carriers. A DRD2 haplotype analysis in the same sample confirmed these results, indicating an association between high D2 density and increased task-switching effort. Our results provide evidence that converges with that from association studies relating increased D2 density to deficits in cognitive flexibility in schizophrenia. We suggest that individual differences in striatal D2 signaling in healthy humans modulate goal-directed gating to prefrontal cortex, thus leading to individual differences in switching intentionally to newly relevant behaviors.
2009
One of the most important factors controlling material specific processing in the human brain is language dominance, i.e. hemispheric specialization in semantic processes. Although previous studies have shown that lateralized long-term memory processes in the medial temporal lobes are modified in subjects with atypical (right) language dominance, the effect of language dominance on the neural basis of working memory (WM) has remained unknown. Here, we used functional MRI (fMRI) to study the impact of language dominance on the neural representation of WM. We conducted an n-back task in three different load conditions and with both verbal and nonverbal (spatial) material in matched groups of left and right language dominant subjects. This approach allowed us to investigate regions showing significant interactions between language dominance and material. Overall, right dominant subjects showed an increased inter-individual variability of WM-related activations. Verbal WM involved more pronounced activation of the left fusiform cortex in left dominant subjects and of the right inferior parietal lobule in the right dominant group. Spatial WM, on the other hand, induced activation of right hemispheric regions in left dominant subjects, but no specific activations in right dominant subjects. Taken together, these findings indicate that the neural basis of verbal WM processes depends on language dominance and is more mutable in right dominant subjects. The increased variability in right dominant subjects strongly suggests that a standard network of material-dependent WM processes exists in left dominant subjects, and that right dominant subjects use variable alternative networks.
We experimentally demonstrate how “unpacking” provides a possible approach for mitigating the dilemma of public goods provision through private contributions. Subjects' total contributions increase when a single public good is split into two identical public goods.
We found that personality characteristics are linked to dissociable connectivity streams in the human brain. Whereas fiber tracts between a subcortical network, including the hippocampus and amygdala, and the ventral striatum predicted individual differences in novelty seeking, tracts between prefrontal cortex and the striatum predicted individual differences in reward dependence. These findings suggest that the strength of limbic-striatal connectivity may, in part, underlie human personality traits.
This article complements the experimental literature that has shown the importance of reciprocity for behaviour in stylised labour markets or other decision settings. We use individual measures of reciprocal inclinations in a large, representative survey and relate reciprocity to real world labour market behaviour and life outcomes. We find that reciprocity matters and that the way in which it matters is very much in line with the experimental evidence. In particular, positive reciprocity is associated with receiving higher wages and working harder. Negatively reciprocal inclinations tend to reduce effort. Negative reciprocity increases the likelihood of being unemployed.
Many economic decisions involve a substantial amount of uncertainty, and therefore crucially depend on how individuals process probabilistic information. In this paper, we investigate the capability for probability judgment in a representative sample of the German population. Our results show that almost a third of the respondents exhibits systematically biased perceptions of probability. The findings also indicate that the observed biases are related to individual economic outcomes, which suggests potential policy relevance of our findings.
Laboratory experiments are a widely used methodology for advancing causal knowledge in the physical and life sciences. With the exception of psychology, the adoption of laboratory experiments has been much slower in the social sciences, although during the past two decades the use of lab experiments has accelerated. Nonetheless, there remains considerable resistance among social scientists who argue that lab experiments lack "realism" and generalizability. In this article, we discuss the advantages and limitations of laboratory social science experiments by comparing them to research based on nonexperimental data and to field experiments. We argue that many recent objections against lab experiments are misguided and that even more lab experiments should be conducted.
NeuroCog FX, a computerized neuropsychological screening instrument for serial examinations of patients with epilepsy and other neurological diseases, was developed to fill the gap between unspecific ratings and comprehensive assessments. Eight subtests address attention, working memory, verbal and figural memory, and language. The test duration is less than 30min. In research contexts, the test can be applied at multiple sites by nonacademic personnel. Normative data were recorded from healthy subjects (N=244, age range=16-75years; retest: N=44; validation: N=40) and unselected patients from an epileptology unit (N=212; retest: N=94; validation: N=126). Psychometric analyses confirmed sufficient reliability and concurrent validity, particularly in patients. NeuroCog FX memory and overall performance scores showed "fair" to "good" diagnostic utility with respect to deficits revealed by established tests. NeuroCog FX provides reliable and valid measures of cognitive performance and may be used in clinical and research contexts as a screening instrument.
In humans, presence of an A1 allele of the DRD2/ANKK1-TaqIa polymorphism is associated with reduced expression of dopamine (DA) D(2) receptors in the striatum. Recently, it was observed that carriers of the A1 allele (A1+ subjects) showed impaired learning from negative feedback in a reinforcement learning task. Here, using functional MRI (fMRI), we investigated carriers and noncarriers of the A1 allele while they performed a probabilistic reversal learning task. A1+ subjects showed subtle deficits in reversal learning. In particular, these deficits consisted of an impairment in sustaining the newly rewarded response after a reversal and in a generally decreased tendency to stick with a rewarded response. Both genetic groups showed increased fMRI signal in response to negative feedback in the rostral cingulate zone (RCZ) and anterior insula. Negative feedback that incurred a change in behavior additionally engaged the ventral striatum and a region of the midbrain consistent with the location of dopaminergic cell groups. The response of the RCZ to negative feedback increased as a function of preceding negative feedback. However, this graded response was not observed in the A1+ group. Furthermore, the A1+ group also showed diminished recruitment of the right ventral striatum and the right lateral orbitofrontal cortex (lOFC) during reversals. Together, these results suggest that a genetically driven reduction in DA D(2) receptors leads to deficient feedback integration in RCZ. This, in turn, was accompanied by impaired recruitment of the ventral striatum and the right lOFC during reversals, which might explain the behavioral differences between the genetic groups.
A novel approach which conjoins elements of experimental macroeconomics and behavioral finance allows us to study the components of industrial firms' currency trade decisions in the controlled environment of a laboratory. We analyze how firms operate in the currency market in a deterministic two-country model with two currencies. Consistent with presumptions of real-world behavior, subjects in our experiment tend to base their trade decisions on definite rather than on uncertain key data: Interest rates have a high impact, while technical analysis plays a minor role. We finally demonstrate how a simple decision rule that incorporates our findings might outperform the actually observed trade decisions.
Previous studies have shown that prolonged inspection of a tilted visual pattern leads to changes in perception ("tilt after-effect", TAE), as well as to a reduction of the neural activation evoked by this pattern ("neural adaptation"). In this fMRI study, we investigated whether such perceptual and neural adaptation can be induced solely by mental imagination. The subjects were asked to mentally generate tilted lines, after which they were presented test lines oriented in the same or the direction orthogonal to the mentally tilted lines. Subjects showed a TAE even after mental imagery ("mental TAE"). Furthermore, a significant orientation-specific adaptation occurred in extrastriate visual areas (V3-V4), showing a decreasing gradient of adaptation from areas V4 to V1. Both this neural adaptation and the individual size of the mental TAE correlated with performance in a behavioural task probing mental imagery. Thus, orientation-selective neurons in visual areas seem to be recruited by mental imagery, and the amount of recruitment correlates with the degree of success of mental imagery operations. The influence of mental imagery on perception and on the neural activity in extrastriate visual areas provides evidence for analogue coding of mental images.
Background. The role of the brain-derived neurotrophic factor (BDNF) in the pathogenesis of affective disorders such as depression has been controversial. Mounting evidence comes from structural imaging, that the functional BDNF Val66Met polymorphism influences the hippocampal volume with carriers of the 66Met allele (Val/Met and Met/Met group) having smaller hippocampi. Given that stress-induced atrophy of the hippocampus is associated with the pathogenesis of affective disorders, the functional BDNF Val66Met polymorphism could be an incremental risk factor. Method. Eighty-seven healthy Caucasian participants underwent structural imaging and were genotyped for the BDNF Val66Met polymorphism. Data were analysed by means of voxel-based morphometry (VBM). Results. Region of interest (ROI) analyses revealed an association between the 66Met allele and smaller parahippo- campal volumes and a smaller right amygdala. In addition, the whole-brain analysis showed that the thalamus, fusiformus gyrus and several parts of the frontal gyrus were smaller in 66Met allele carriers. Conclusions. This study demonstrates that the impact of the BDNF Val66Met polymorphism is not confined to the hippocampus but also extends to the parahippocampal gyrus and the amygdala.
BACKGROUND: How many patient deaths the teams at palliative care units can cope with, the supporting factors in coping and the future prospects of the teams have not yet been subject to research in Germany. The aim of the study was to assess burden factors, burden symptoms and protective factors, the critical number and distribution of patient deaths as well as the prospects of the teams. SAMPLE AND METHODS: A total of 873 members of palliative care teams from 95 (60% of n=158) German palliative care units took part in this explorative evaluation. Basic factors could be identified using factor analysis. Differences between professional groups were checked with analysis of variance. RESULTS: Results showed that not having reached the objectives of palliative care was the central burden factor. In the majority of cases a team reacted by being loquacious. The team itself was ranked as the most important protective factor. The mean critical number of deaths was 4.4 per week. Consecutive patient deaths were rated as being significantly more stressful than evenly spread deaths. Ratings for the future prospects of the team were significantly lower in teams where not meeting the objectives of palliative care was considered a high burden factor. CONCLUSION: A clearer definition of the objectives of palliative care and support of team communication are desirable.
Evaluative-feedback, occurring in our daily life, generally contains subjective appraisal of one's specific abilities and personality characteristics besides objective right-or-wrong information. Traditional psychological researches have proved it to be important in building up one's self-concept; however, the neural basis underlying its cognitive processing remains unclear. The present neuroimaging study revealed the mechanism of evaluative-feedback processing at the neural level. 19 healthy Chinese subjects participated in this experiment, and completed the time-estimation task to better their performance according to four types of feedback, namely positive evaluative- and performance-feedback as well as negative evaluative- and performance-feedback. Neuroimaging findings showed that evaluative- rather than performance-feedback can induce increased activities mainly distributed in the cortical midline structures (CMS), including medial prefrontal cortex (BA 8/9)/anterior cigulate cortex (ACC, BA 20), precuneus (BA 7/31) adjacent to posterior cingulate gyrus (PCC, BA 23) of both hemispheres, as well as right inferior lobule (BA 40). This phenomenon can provide evidence that evaluative-feedback may significantly elicit the self-related processing in our brain. In addition, our results also revealed that more brain areas, particularly some self-related neural substrates were activated by the positive evaluative-feedback, in comparative with the negative one. In sum, this study suggested that evaluative-feedback was closely correlated with the self-concept processing, which distinguished it from the performance-feedback.
The role of the prefrontal Cortex (PFC) in higher cognitive functions - including working memory, conflict resolution, set shifting and semantic processing - has been demonstrated unequivocally. Despite the great heterogeneity among tasks measuring these phenotypes, due in part to the different cognitive sub-processes implied and the specificity of the stimulus material used, there is agreement that all of these tasks recruit an executive control system located in the PFC. On a biochemical level it is known that the dopaminergic system plays an important role in executive control functions. Evidence comes from molecular genetics relating the functional COMT Val158Met polymorphism to working memory and set shifting. In order determine whether this pattern of findings generalises to linguistic and semantic processing, we investigated the effects of the COMT Val158Met polymorphism in lexical decision making using masked and unmasked versions of the semantic priming paradigm on N = 104 healthy subjects. Although we observed strong priming effects in all conditions (masked priming, unmasked priming with short/long stimulus asynchronies (SOAs), direct and indirect priming), COMT was not significantly related to priming, suggesting no reliable influence on semantic processing. However, COMT Val158Met was strongly associated with lexical decision latencies in all priming conditions if considered separately, explaining between 9 and 14.5% of the variance. Therefore, the findings indicate that COMT mainly influences more general executive control functions in the PFC supporting the speed of lexical decisions.
Recent findings have highlighted the importance of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, 32 kDa), a key regulatory molecule in the dopaminergic signalling pathway for dopamine related phenotypes like antisocial-behavior, drug addiction and schizophrenia. This is the first study investigating the role of the DARPP-32 gene for personality. In a sample of n=838 healthy German Caucasian subjects we found a significant association between rs907094 and ANGER. Carriers of the T-allele showed significantly higher ANGER scores than participants without a T-allele (F((1,837))=9.52, p=0.002). In a second step we validated self-report data of ANGER by investigating their relation to structural brain differences in anger-related brain regions using voxel-based morphometry. A negative association between ANGER scores and the volume of the left amygdala could be detected. The present findings yield genetic evidence for the importance of dopaminergic signal transduction for the personality trait of ANGER. In addition volumetric MRI data support the role of the amygdala for the processing of anger.
Temporal lobe epilepsy with hippocampus sclerosis (HS) is the most frequent focal epilepsy and often refractory to anticonvulsant therapy. Secondary structural damage has been reported in several studies of temporal lobe epilepsy and unilateral hippocampal sclerosis. Applying diffusion tensor imaging (DTI) we investigated alterations in white matter following temporal lobe surgery in patients with medial temporal lobe epilepsy. We examined 40 patients who underwent surgery at our hospital for HS between 1996 and 2006 with diffusion tensor imaging (DTI). Images were obtained at a 3 T MRI scanner employing 60 gradient directions. Tract-based spatial statistics (TBSS), a novel voxel-based approach, was applied to analyze the data. Both patients with left- as well as right-sided surgery exhibited widespread degradation of fractional anisotropy (FA) in main fiber tracts not limited to the respective temporal lobe such as the uncinate fasciculus, the fronto-occipital fasciculus, the superior longitudinal fasciculus, the corpus callosum and the corticospinal tract on the respective hemisphere. Patients with left-hemispheric surgery showed more widespread affections ipsilaterally and also FA decrease in the contralateral inferior longitudinal fasciculus. DTI demonstrates widespread clusters of abnormal diffusivity and anisotropy in prominent white matter tracts linking mesial temporal lobe structures with other brain areas. Alterations in the ipsilateral mesial temporal lobe can be attributed to be a result of surgery, whereas extratemporal FA decrease is more likely the result of the underlying seizure disorder.
A lot is known about the neural basis of directing attention based on explicit cues. In real life however, attention shifts are rarely directed by explicit cues but rather generated implicitly, for example on the basis of previous experience with a given situation. Here, we aimed at studying attention shifts dependent on recent trial history. While explicitly cued attention shifts involve activity in cortex of the intraparietal sulcus, whether this region is also involved in shifting attention according to recent history is still unknown. We asked observers to detect targets in a stream of visual stimuli with three feature dimensions: color, shape and motion. Critically, target occurrence probability was always higher in one stimulus dimension than in the others, and probabilities switched between dimensions over blocks of trials. After each probability switch, target detection times decreased exponentially for high-probability targets and increased for low-probability targets, compatible with gradual shifts in attention dependent on trial history since the switch. BOLD signal in left prefrontal and intraparietal sulcus regions was higher in the early phase after the switch, while anterior cingulate, cuneus, precuneus, temporal and more anterior frontal regions showed more activation later after the switch. These findings are compatible with the engagement of regions involved in the establishment and maintenance of attentional sets. BOLD signal in left intraparietal sulcus correlated with the size of the performance changes consecutive to the detected targets, suggesting that it reflects the size of attention shifts induced by updating target probabilities over recent trial history.
The ability to perceive facial motion is important to successfully interact in social environments. Previously, imaging studies have investigated neural correlates of facial motion primarily using abstract motion stimuli. Here, we studied how the brain processes natural non-rigid facial motion in direct comparison to static stimuli and matched phase-scrambled controls. As predicted from previous studies, dynamic faces elicit higher responses than static faces in lateral temporal areas corresponding to hMT+/V5 and STS. Interestingly, individually defined, static-face-sensitive regions in bilateral fusiform gyrus and left inferior occipital gyrus also respond more to dynamic than static faces. These results suggest integration of form and motion information during the processing of dynamic faces even in ventral temporal and inferior lateral occipital areas. In addition, our results show that dynamic stimuli are a robust tool to localize areas related to the processing of static and dynamic face information.
Dopamine modulates complex cognitive functions like working memory and cognitive control. It is widely accepted that an optimal level of prefrontal dopamine supports working memory performance. In the present study we used a molecular genetic approach to test whether the optimal activity of the dopamine system for different component processes of working memory is additionally related to the availability of dopamine D2 receptors. We sought evidence for this assumption by investigating the interaction effect (epistasis) of variations in two dopaminergic candidate genes: the catechol-O-methyltransferase (COMT) Val(158)Met polymorphism, which has been shown to influence prefrontal dopamine concentration, and the DRD2/ANKK1-Taq-Ia polymorphism, which has been related to the density of D2 receptors. Our results show that COMT effects on working memory performance are modulated by the DRD2/ANKK1-TAQ-Ia polymorphism and the specific working memory component process under investigation. Val-participants--supposedly characterized by increased prefrontal dopamine concentrations--outperformed Val+ participants in the manipulation of working memory contents, but only when D2 receptor density could be considered to be high. No such effect was present for passive maintenance of working memory contents or for maintenance in the face of distracting information. This beneficial effect of a balance between prefrontal dopamine availability and D2 receptor density reveals the importance of considering epistasis effects and different working memory subprocesses in genetic association studies.
Behavioral economists have proposed that money illusion, which is a deviation from rationality in which individuals engage in nominal evaluation, can explain a wide range of important economic and social phenomena. This proposition stands in sharp contrast to the standard economic assumption of rationality that requires individuals to judge the value of money only on the basis of the bundle of goods that it can buy – its real value – and not on the basis of the actual amount of currency – its nominal value. We used fMRI to investigate whether the brain's reward circuitry exhibits money illusion. Subjects received prizes in 2 different experimental conditions that were identical in real economic terms, but differed in nominal terms. Thus, in the absence of money illusion there should be no differences in activation in reward-related brain areas. In contrast, we found that areas of the ventromedial prefrontal cortex (vmPFC), which have been previously associated with the processing of anticipatory and experienced rewards, and the valuation of goods, exhibited money illusion. We also found that the amount of money illusion exhibited by the vmPFC was correlated with the amount of money illusion exhibited in the evaluation of economic transactions.
PURPOSE: Several small patient studies and case reports raise concerns that the reliability of functional magnetic resonance imaging (fMRI) may be impaired in the vicinity of cerebral lesions. This could affect the clinical validity of fMRI for presurgical language lateralization. The current study sets out to identify if a systematic effect of lesion type and localization on fMRI exists. METHODS: We classify lesions typically occurring in epilepsy patients according to (1) their potential to disturb blood oxygenation level dependent (BOLD)-effect generation or detection or to disturb spatial brain normalization, and (2) the proximity of lesions to protocol-specific volumes of interest (VOIs). The effect of lesions is evaluated through the examination of 238 epilepsy patients and a subgroup of 37 patients with suspected unilateral left-language dominance according to the Wada test. RESULTS: Patients with fMRI-critical lesions such as cavernomas, gliomas, and mass defects close to VOIs, or with severe atrophy, show lower lateralization indices (LIs) and more often discordant language lateralization with the Wada test than do patients without such lesions. DISCUSSION: This study points seriously toward fMRI-language lateralization being sensitive to cerebral lesions. Some lesion types and locations are more critical than others. Our results question the noncritical application of fMRI in patients with cerebral lesions.
2008
Flexibly adapting behavior in dynamic environments relies on fronto-limbic networks that include the amygdala, orbitofrontal cortex, and striatum. Animal work demonstrates that interactions among these regions are critical for flexible feedback-guided learning, but it remains unknown to what extent such anatomical–functional interactions operate in humans. Here, we use connectivity analyses in both structural and functional MRI to further our understanding of how brain circuits work in conjunction to promote goal-directed behavior. In particular, fiber tracking based on diffusion-weighted imaging provides information about anatomical connectivity between brain structures, and functional MRI provides estimates of functional connectivity between structures. We found that, during a feedback-guided reversal learning task, the strength of estimated white matter tracts from the amygdala to the hippocampus, orbitofrontal cortex, and ventral striatum predicted both how subjects adapted their behavior following positive and negative feedback, and the functional connectivity (estimated from functional MRI time series) between the amygdala and these regions. In addition, we identified a dissociation between an amygdala-hippocampus circuit that predicted response switching, and an amygdala-orbitofrontal cortex circuit that predicted learning following rule reversals. These findings provide novel insights into how the anatomy and functioning of amygdala-related brain circuits mediate different aspects of feedback-guided learning behavior.
This paper provides evidence about the determinants of trust and reciprocal inclinations, that is, a tendency for people to respond in kind to hostile or kind actions, in a representative setting. We investigate the prevalence of reciprocity in the population, the correlation between trust and positive and negative reciprocal inclinations within person, the individual determinants of reciprocity, and the relationship with psychological measures of personality. We find that most people state reciprocal inclinations, in particular in terms of positive reciprocity, as well as substantial heterogeneity in the degree of trust and reciprocity. Trust and positive reciprocity are only weakly correlated, while trust and negative reciprocity exhibit a negative correlation. In terms of determinants, being female and increasing age are associated with stronger positive and weaker negative reciprocal tendencies. Taller people are more positively reciprocal, but height has no impact on negative reciprocity. Psychological traits also affect trust and reciprocity.
Many economic decisions involve a substantial amount of uncertainty. Therefore it is crucial for economists to understand how people process probabilistic information. In this paper, we measure the capability for probability judgment in a representative sample of the German population. Our results show that almost a third of the respondents exhibits biased probability judgment. Moreover, the distribution of judgment biases in the population is systematic. Finally, we show that the observed biases have a significantly negative impact on individual economic outcomes. Our findings have straightforward policy implications for the labor market and for debt counseling services.
We present a cellular neuronal network (CNN) based approach to classify magnetic resonance images with and without hippocampal or Ammon’s horn sclerosis (AHS) in the medial temporal lobe. A CNN combines the architecture of cellular automata and artificial neural networks and is an array of locally coupled nonlinear electrical circuits or cells, which is capable of processing a large amount of information in parallel and in real time. Using an exemplary database that consists of a large number of volumes of interest extracted from T1-weighted magnetic resonance images from 144 subjects we here demonstrate that the network allows to classify brain tissue with respect to the presence or absence of mesial temporal sclerosis. Results indicate the general feasibility of CNN-based computer-aided systems for diagnosis and classification of images generated by medical imaging systems.
Recently developed models of fairness can explain a wide variety of seemingly contradictory facts. One of the most controversial and yet unresolved issues in the modeling of fairness preferences concerns the behavioral relevance of fairness intentions. Intuitively, fairness intentions seem to play an important role in economic relations, political struggles, and legal disputes but there is surprisingly little direct evidence for its behavioral importance. We provide experimental evidence for the behavioral relevance of fairness intentions in this paper. Our main result indicates that the attribution of fairness intentions is important in both the domains of negatively and positively reciprocal behavior. This means that equity models exclusively based on preferences over the distribution of material payoffs cannot capture reciprocal behavior. Models that take players' fairness intentions and distributional preferences into account are consistent with our data, while models that focus exclusively on intentions or on the distribution of material payoffs are not.
We provide evidence on how two important types of institutions -- dismissal barriers, and bonus pay-- affect contract enforcement behavior in a market with incomplete contracts and repeated interactions.Dismissal barriers are shown to have a strong negative impact on worker performance, and marketefficiency, by interfering with firms' use of firing threat as an incentive device. Dismissal barriersalso distort the dynamics of worker effort levels over time, cause firms to rely more on the spot marketfor labor, and create a distribution of relationship lengths in the market that is more extreme, withmore very short and more very long relationships. The introduction of a bonus pay option dramaticallychanges the market outcome. Firms are observed to substitute bonus pay for threat of firing as an incentivedevice, almost entirely offsetting the negative incentive and efficiency effects of dismissal barriers.Nevertheless, contract enforcement behavior remains fundamentally changed, because the option topay bonuses causes firms to rely less on long-term relationships. Our results show that market outcomesare the result of a complex interplay between contract enforcement policies and the institutions in whichthey are embedded.
Chorea-acanthocytosis (ChAc) is a rare autosomal recessive neurodegenerative disease with erythrocyte membrane dysfunction, progressive hyperkinesia, and neuropsychological abnormalities. Neuropathologic and neuroimaging investigations demonstrate damage to the basal ganglia. Here, a novel automated technique of voxel-based magnetic resonance imaging (MRI) analysis was applied to determine the volumes of caudate nucleus and putamen in nine patients with proven ChAc in comparison with 257 healthy controls. At individual subject level, ChAc patients and controls could be reliably discriminated by the volume of the caudate, using a cut-off of 5 ml, or by a value of −3 in terms of z scores. Putaminal volumes were also significantly reduced in ChAc patients, but showed some overlap with controls. The results indicate that this new automated volumetric MRI analysis offers an objective imaging tool for identification of ChAc patients by quantification of basal ganglia atrophy and lends itself to extension to other basal ganglia diseases.
We study strategic voting in a laboratory experiment using a Borda mechanism. We find that manipulation rates are surprisingly low, even for individuals who know that they possess superior information about the other agents’ preferences. Exploring possible explanations, we find that manipulation rates rise significantly if individuals are not only informed about the other agents’ preferences but also about their actual votes. This suggests that uncertainty plays a key role in understanding strategic behavior in elections. By contrast, distributional concerns, e.g., in the form of inequality aversion, are found to play a negligible role in our context.
Mounting evidence shows that the brain derived neurotrophic factor (BDNF) plays a crucial role in synaptic plasticity. Due to its potential involvement in psychiatric diseases like depression and anxiety disorders BDNF lately became a major target in research. A functional variant of the BDNF gene – the BDNF Val66Met polymorphism – is of particular interest, because it influences the BDNF secretion which is followed by signaling at the TrkB receptor leading to dendritic growth of neurons. Findings from genetic association studies in humans yield heterogenous results with respect to the question of which allele represents a potential risk factor for an affective disorder. Although structural MRT studies revealed that the 66Met variant is associated with smaller hippocampi and could therefore present the risk allele, fMRI studies investigating the processing of emotion with respect to the BDNF Val66Met polymorphism are lacking.
N = 37 healthy female subjects participated in an fMRI experiment with an affective startle reflex paradigm. Carriers of the 66Met variant showed stronger amygdala activation in the right hemisphere in response to emotional stimuli compared to neutral stimuli. The results of this study add to growing literature, showing that it is the 66Met, which is associated with higher trait anxiety.
Theta oscillations in the medial temporal lobe (MTL) of mammals are involved in various functions such as spatial navigation, sensorimotor integration, and cognitive processing. While the theta rhythm was originally assumed to originate in the medial septum, more recent studies suggest autonomous theta generation in the MTL. Although coherence between entorhinal and hippocampal theta activity has been found to influence memory formation, it remains unclear whether these two structures can generate theta independently. In this study we analyzed intracranial electroencephalographic (EEG) recordings from 22 patients with unilateral hippocampal sclerosis undergoing presurgical evaluation prior to resection of the epileptic focus. Using a wavelet-based, frequency-band-specific measure of phase synchronization, we quantified synchrony between 10 different recording sites along the longitudinal axis of the hippocampal formation in the non-epileptic brain hemisphere. We compared EEG synchrony between adjacent recording sites (i) within the entorhinal cortex, (ii) within the hippocampus, and (iii) between the hippocampus and entorhinal cortex. We observed a significant interregional gap in synchrony for the delta and theta band, indicating the existence of independent delta/theta rhythms in different subregions of the human MTL. The interaction of these rhythms could represent the temporal basis for the information processing required for mnemonic encoding and retrieval.
Shape perception is important for object recognition. However, behavioral studies have shown that rigid motion also contributes directly to the recognition process, in addition to providing visual cues to shape. Using psychophysics and functional brain imaging, we investigated the neural mechanisms involved in shape and motion processing for dynamic object recognition. Observers discriminated between pairs of rotating novel objects in which the 3-dimensional shape difference between the pair was systematically varied in metric steps. In addition, the objects rotated in either the same or the different direction to determine the effect of task-irrelevant motion on behavior and neural activity. We found that observers' shape discrimination performance increased systematically with shape differences, as did the hemodynamic responses of occipitotemporal, parietal, and frontal regions. Furthermore, responses in occipital regions were only correlated with observers' perceived shape differences. We also found different effects of object motion on shape discrimination across observers, which were reflected in responses of the superior temporal sulcus. These results suggest a network of regions that are involved in the discrimination of metric shape differences for dynamic object recognition.
Purpose
Functional magnetic resonance imaging (fMRI) is being used increasingly for language dominance assessment in the presurgical work-up of patients with pharmacoresistant epilepsy. However, the interpretation of bilateral fMRI-activation patterns is difficult. Various studies propose fMRI-lateralization index (LI) thresholds between ±0.1 and ±0.5 for discrimination of atypical from typical dominant patients. This study examines if these thresholds allow identifying atypical dominant patients with sufficient safety for presurgical settings.
Methods
65 patients had a tight comparison, fully controlled semantic decision fMRI-task and a Wada-test for language lateralization. According to Wada-test, 22 were atypical language dominant. In the remaining, Wada-test results were compatible with unilateral left dominance. We determined fMRI-LI for two frontal and one temporo-parietal functionally defined, protocol-specific volume of interest (VOI), and for the least lateralized of these VOIs (“low-VOI”) in each patient.
Results
We find large intra-individual LI differences between functionally defined VOIs irrespective of underlying type of language dominance (mean LI difference 0.33 ± 0.35, range 0–1.6; 15% of patients have inter-VOI-LI differences >1.0). Across atypical dominant patients fMRI-LI in the Broca's and temporo-parietal VOI range from −1 to +1, in the “remaining frontal” VOI from −0.93 to 1. The highest low-VOI-LI detected in atypical dominant patients is 0.84.
Conclusions
Large intra-individual inter-VOI-LI differences and strongly lateralized fMRI-activation in patients with Wada-test proven atypical dominance question the value of the proposed fMRI-thresholds for presurgical language lateralization. Future studies have to develop strategies allowing the reliable identification of atypical dominance with fMRI. The low-VOI approach may be useful.
2007
This paper investigates to what extent individuals' risk preferences are correlated with the cross-sectional earnings risk of their occupation. We exploit data from the German Socio-Economic Panel, which contains a direct survey question about willingness to take risks that has been shown to be a behaviorally valid measure of risk aversion. As a measure of earnings risk, we use the cross-sectional variation in earnings that is left unexplained by human capital variables in Mincerian wage regressions. Our evidence shows that individuals with low willingness to take risks are more likely to work in occupations with low earnings risk. This pattern is found regardless of the level of occupation categories, region, gender and labor market experience.
Dopamine is critical for reward‐based decision making, yet dopaminergic drugs can have opposite effects in different individuals. This apparent discrepancy can be accounted for by hypothesizing an ‘inverted‐U’ relationship, whereby the effect of dopamine agents depends on baseline dopamine system functioning. Here, we used functional MRI to test the hypothesis that genetic variation in the expression of dopamine D2 receptors in the human brain predicts opposing dopaminergic drug effects during reversal learning. We scanned 22 subjects while they engaged in a feedback‐based reversal learning task. Ten subjects had an allele on the Taq1A DRD2 gene, which is associated with reduced dopamine receptor concentration and decreased neural responses to rewards (A1+ subjects). Subjects were scanned twice, once on placebo and once on cabergoline, a D2 receptor agonist. Consistent with an inverted‐U relationship between the DRD2 polymorphism and drug effects, cabergoline increased neural reward responses in the medial orbitofrontal cortex, cingulate cortex and striatum for A1+ subjects but decreased reward responses in these regions for A1– subjects. In contrast, cabergoline decreased task performance and fronto‐striatal connectivity in A1+ subjects but had the opposite effect in A1– subjects. Further, the drug effect on functional connectivity predicted the drug effect on feedback‐guided learning. Thus, individual variability in how dopaminergic drugs affect the brain reflects genetic disposition. These findings may help to explain the link between genetic disposition and risk for addictive disorders.
This study reports evidence from a field experiment that was conducted to investi- gate the relevance of gift exchange in a natural setting. In collaboration with a chari- table organization, we sent roughly 10,000 solicitation letters to potential donors. One- third of the letters contained no gift, one-third contained a small gift, and one-third contained a large gift. Treatment assignment was random. The results confirm the eco- nomic importance of gift exchange. Compared to the no gift condition, the relative frequency of donations increased by 17 percent if a small gift was included and by 75 percent for a large gift. The study extends the current body of research on gift exchange, which is almost exclusively confined to laboratory studies.
Event-related functional Magnetic Resonance Imaging (fMRI) allows for the comparison of hemodynamic responses evoked by items that are remembered in a subsequent memory task vs. items that are forgotten. In this way, brain regions that assumingly contribute to successful memory encoding have been identified, including the left inferior prefrontal cortex (LIPC) and the medial temporal lobe. Although a cerebellar involvement in verbal working memory is well-established, a contribution of the cerebellum to episodic long-term encoding has only sporadically been described, and mechanisms underlying cerebellar memory effects are unclear. We conducted a typical incidental verbal memory fMRI experiment with three different encoding tasks varying the depth of semantic processing. Slice positioning allowed for the coverage of the entire cerebellum. We observed a significant subsequent memory effect within the superior and posterior right cerebellar hemisphere that was task independent. Additionally, we found a different area within the superior right cerebellum displaying a memory effect specifically for semantically processed words and a bilateral cerebellar activation specifically associated with encoding success only for a non-semantic task. Our results suggest that besides its known role in verbal working memory, the cerebellum contributes to episodic long-term encoding and should therefore be considered in future fMRI studies dealing with episodic memory.
Whether social comparison affects individual well-being is of central importance for understanding behavior in any social environment. Traditional economic theories focus on the role of absolute rewards, whereas behavioral evidence suggests that social comparisons influence well-being and decisions. We investigated the impact of social comparisons on reward-related brain activity using functional magnetic resonance imaging (fMRI). While being scanned in two adjacent MRI scanners, pairs of subjects had to simultaneously perform a simple estimation task that entailed monetary rewards for correct answers. We show that a variation in the comparison subject’s payment affects blood oxygenation level–dependent responses in the ventral striatum. Our results provide neurophysiological evidence for the importance of social comparison on reward processing in the human brain.
The functional deficits associated with hippocampal sclerosis during declarative memory formation are largely unknown. In this study, we analyzed intracranial event-related potentials recorded from the medial temporal lobes of nine epilepsy patients performing a word memorization task. We used frequency-specific wavelet analysis to assess stimulus-related changes in power and intertrial phase coherence. Statistical analysis revealed a significant decrease of stimulus-induced power in the δ and θ range on the side of pathology. No significant differences in phase locking were observed. Findings indicate a reduced availability of recruitable neural assemblies not only in the hippocampus but also in the rhinal cortex during memory formation. Network functions related to the timing of neural responses to the stimulus appear to be preserved.
Human decision making has become one of the major research-foci in economics, marketing and in neuroscience. This study integrates perspectives from these disciplines by examining neurophysiological correlates to Reference-dependence of utility evaluations in real market contexts both before and after choice. First, by comparing buying and selling decisions, we observe an activation of the amygdala only in the latter. We interpret this as loss aversion with respect to prior possessions. This finding contributes to the settling of an ongoing fundamental dispute in economic theory by indicating the absence of loss aversion for money in routine transactions. Second, ex post satisfaction statements are accompanied by an activation of the reward processing orbitofrontal cortex, if the evaluation context is framed by a high external reference price instead of a lower internal reference price. This indicates a nonrational Reference-dependence – despite the neoclassical view of a rational Homo Economicus – of satisfaction measures and challenges a central marketing variable.
Neuropsychological and neuroimaging data have shown a functional lateralization of the medial temporal lobes for verbal and non-verbal memory material respectively. We hypothesized that this lateralization is related to language lateralization. Using fMRI we conducted three memory tasks with different memory material (words, faces, landscape images) alongside with a paradigm for the determination of language dominance in 44 healthy subjects. We included left as well as right-handed subjects because persons with atypical language dominance are known to be overrepresented in the group of left-handers. Lateralization indices for the BOLD activation in the medial temporal lobes from the memory tasks were correlated with those for the language task. We show that the material-specific lateralization is related to language dominance such that verbal encoding shows strong positive relation to language dominance whereas face encoding shows the opposite effect. Our data provide first fMRI evidence for a relation between language dominance and material specificity of the medial temporal lobes for memory functions. We suggest that the language-dominant hemisphere is more strongly engaged in memory processing of verbal material. These data provide grounds for the investigation of pathological changes in this relationship due to cortical dysfunctions.
The medial temporal lobes (MTLs) are essential for both encoding and retrieval processes in declarative memory. In addition, they are a frequent seizure focus for medically refractory epilepsy. One of the major side effects of MTL resection is a decline in memory functions. Most functional imaging paradigms have been developed to find preoperative measures that, to obtain a prognosis of postoperative memory performance, employ explicit memory encoding strategies to elicit MTL activation, and require a great amount of cognitive effort. We applied three different implicit encoding tasks, which require less effort and time, to a group of healthy subjects. We found left-lateralized activation for verbal stimuli, bilateral activation for pictures, and right-lateralized activation for faces. The present study shows that even with an implicit memory-encoding paradigm, a lateralized activation of MTL structures can be achieved. This may lead to paradigms for routine clinical application that require less cognitive effort and time on the part of patients.
We analysed the influence of mesial temporal lobe epilepsy on the thickness of the corpus callosum (CC) in a large sample of well-characterized patients (n = 96) and healthy controls (n = 28). In particular, we investigated whether callosal structures are differentially affected depending on the affected hemisphere and age of epilepsy onset. Overall, we observed that epilepsy is associated with a decreased thickness in posterior callosal regions. Patients with an early onset, especially patients with left onset, additionally exhibited a smaller callosal thickness in more anterior and midbody regions. These findings may reflect non-specific as well as specific effects of temporal lobe epilepsy on CC development and interhemispheric connectivity.
2006
People are reciprocal if they reward kind actions and punish unkind ones. In this paper we present a formal theory of reciprocity. It takes into account that people evaluate the kindness of an action not only by its consequences but also by its underlying intention. The theory is in line with the relevant stylized facts of a wide range of experimental games, such as the ultimatum game, the gift-exchange game, a reduced best-shot game, the dictator game, the prisoner's dilemma, and public goods games. Furthermore, it predicts that identical consequences trigger different reciprocal responses in different environments. Finally, the theory explains why outcomes tend to be fair in bilateral interactions whereas extremely unfair distributions may arise in competitive markets.
People are reciprocal if they reward kind actions and punish unkind ones. In this paper we present a formal theory of reciprocity. It takes into account that people evaluate the kindness of an action not only by its consequences but also by its underlying intention. The theory is in line with the relevant stylized facts of a wide range of experimental games, such as the ultimatum game, the gift-exchange game, a reduced best-shot game, the dictator game, the prisoner's dilemma, and public goods games. Furthermore, it predicts that identical consequences trigger different reciprocal responses in different environments. Finally, the theory explains why outcomes tend to be fair in bilateral interactions whereas extremely unfair distributions may arise in competitive markets.
In a laboratory experiment we show that minimum wages have significant and lasting effects on subjects’ reservation wages. The temporary introduction of a minimum wage leads to a rise in subjects’ reservation wages which persists even after the minimum wage has been removed. Firms are therefore forced to pay higher wages after the removal ofthe minimum wage than before its introduction. As a consequence, the employment effects of removing the minimum wage are significantly smaller than are the effects of its introduction. The impact of mini- mum wages on reservation wages may also explain the anomalously low utiliza- tion ofsubminimum wages ifemployers are given the opportunity to pay less than a minimum wage previously introduced. It may further explain why employers often increase workers’ wages after an increase in the minimum wage by an amount exceeding that necessary for compliance with the higher minimum. At a more general level, our results suggest that economic policy may affect people’s behavior by shaping the perception of what is a fair transaction and by creating entitlement effects.
Concrete words that are readily imagined are better remembered than abstract words. Theoretical explanations for this effect either claim a dual coding of concrete words in the form of both a verbal and a sensory code (dual-coding theory), or a more accessible semantic network for concrete words than for abstract words (context-availability theory). However, the neural mechanisms of improved memory for concrete versus abstract words are poorly understood. Here, we investigated the processing of concrete and abstract words during encoding and retrieval in a recognition memory task using event-related functional magnetic resonance imaging (fMRI). As predicted, memory performance was significantly better for concrete words than for abstract words. Abstract words elicited stronger activations of the left inferior frontal cortex both during encoding and recognition than did concrete words. Stronger activation of this area was also associated with successful encoding for both abstract and concrete words. Concrete words elicited stronger activations bilaterally in the posterior inferior parietal lobe during recognition. The left parietal activation was associated with correct identification of old stimuli. The anterior precuneus, left cerebellar hemisphere and the posterior and anterior cingulate cortex showed activations both for successful recognition of concrete words and for online processing of concrete words during encoding. Additionally, we observed a correlation across subjects between brain activity in the left anterior fusiform gyrus and hippocampus during recognition of learned words and the strength of the concreteness effect. These findings support the idea of specific brain processes for concrete words, which are reactivated during successful recognition.
Atypical, i.e. right hemisphere language dominance is frequently observed in early onset left hemisphere epilepsies. In left mesial temporal lobe epilepsy, where eloquent cortex is not directly involved, it is a matter of debate, to which degree atypical language dominance is driven not only by morphological lesions but also by epileptic dysfunction, and whether atypical dominance is hardwired or not. Taking this as the background this study evaluated the hypothesis that epilepsy driven atypical dominancy might be reversible when seizures are successfully controlled. This was evaluated in patients with left mesial temporal lobe epilepsy, who were atypically language dominant by means of language fMRI before surgery, and became seizure free after left selective amygdalo-hippocampectomy. Three out of 53 consecutive atypically dominant patients with chronic epilepsy fulfilled these criteria. Postoperative follow-up language fMRI indicated reversal of right into left dominance in one patient going along with unexpected losses in verbal memory performance. The two other patients experienced unchanged or even enhancement of the pre-existing dominance pattern, going along with consistent postoperative performance changes in cognition. The data thus provide supporting evidence that atypical language dominance can indeed be functionally driven and moreover that in at least some patients, right hemispheric language can shift-back to the left hemisphere when the driving factor, i.e. seizures, becomes successfully controlled. The results have clinical implications for outcome prediction after brain surgery in atypically dominant patients with epilepsy. However, further research in larger groups of atypically dominant patients is required to identify the conditions under which atypical dominance becomes hardwired and when not.
Various methods have been proposed to calculate a lateralization index (LI) on the basis of functional magnetic resonance imaging (fMRI) data. Most of them are either based on the extent of the activated brain region (i.e., the number of “active” voxels) or the magnitude of the fMRI signal change. The purpose of the present study was to investigate the characteristics of various variants of these approaches and to identify the one that yields the most robust and reproducible results. Robustness was assessed by evaluating the dependence on arbitrary external parameters, reproducibility was assessed by Pearson’s correlation coefficient.
LIs based on active voxels counts at one single fixed statistical threshold as well as LIs based on unthresholded signal intensity changes (i.e., based on all voxels in a region of interest) yielded neither robust nor reproducible laterality results. Instead, the lateralization of a cognitive function was best described by “thresholded” signal intensity changes where the activity measure was based on signal intensity changes in those voxels in a region of interest that exceeded a predefined activation level.
However, not all other approaches should be discarded completely since they have their own specific application fields. First, LIs based on active voxel counts in the form of p-value-dependent lateralization plots (LI = LI(p)) can be used as a straightforward measure to describe hemispheric dominance. Second, LIs based on active voxel counts at variable thresholds (standardized by the total number of active voxels) are a good alternative for big regions of interest since LIs based on signal intensity changes are restricted to small ROIs.
We analyze the consequences of control on motivation in an experimental principalagent game, where the principal can control the agent by implementing a minimum performance requirement before the agent chooses a productive activity. Our results show that control entails hidden costs since most agents reduce their performance as a response to the principal?s controlling decision. Overall, the effect of control on the principal?s payoff is nonmonotonic. When asked for their emotional perception of control, most agents who react negatively say that they perceive the controlling decision as a signal of distrust and a limitation of their choice autonomy. (JEL D82, Z13)
In large early cortical lesions, one of the most devastating consequences is the impaired motor dexterity of the contralateral limb. We present the case of an 8-year-old girl with a large left hemispherical porencephaly. Unlike previous reports, the girl exhibited high dexterity of the contralateral hand with preserved independent finger movements. We performed functional MRI of hand motor functions and diffusion tensor imaging, which revealed activation of the ipsilateral motor cortex and absence of a contralateral corticospinal tract. These observations suggest that by intensive training in early life, a complete transhemispheric shift of motor control with high skills can be achieved.
Asymmetry is a common phenomenon in higher organisms. In humans, the cortical representation of language exhibits a high degree of asymmetry with a prevalence of about 90% of left hemispheric dominance, the underlying mechanisms of which are largely unknown. Another sign that exhibits a form of lateralization is the scalp hair-whorl direction, which is either clockwise or anti-clockwise. The scalp hair-whorl develops from the same germ layer as the nervous system, the ectoderm, between the 10th and 16th week in utero and has been shown to be associated with various neurodevelopmental disorders. Here, we use an established fMRI paradigm to examine the association of a solely biological marker of asymmetry, hair-whorl direction and language lateralization. We show that the mechanism that influences hair-whorl direction and handedness [Klar, A.J.S., 2003. Human handedness and scalp hair-whorl direction develop from a common genetic mechanism. Genetics 1651, 269-276.] also affects cerebral language dominance.
It is well recognized that the incidence of atypical language lateralization is increased in patients with focal epilepsy. The hypothesis that shifts in language dominance are particularly likely when epileptic lesions are located in close vicinity to the so-called language-eloquent areas rather than in more remote brain regions such as the hippocampus has been challenged by recent studies. This study was undertaken to assess the effect of lesions in different parts of the left hemisphere, lesions present during language acquisition, on language lateralization. We investigated 84 adult patients with drug-resistant focal epilepsy with structural lesions and 45 healthy control subjects with an established functional MRI language paradigm. Out of the 84 patients 43 had left hippocampal sclerosis, 13 a left frontal lobe lesion and 28 a left temporal-lateral lesion. All these lesions were likely to have been present during the first years of life during language acquisition. To assess the lateralization of cerebral language representation globally as well as regionally, we calculated lateralization indices derived from activations in four regions of interest (i.e. global, inferior frontal, temporo-parietal and remaining prefrontal). Patients with left hippocampal sclerosis showed less left lateralized language representations than all other groups of subjects (P < 0.005). This effect was independent of the factor of region, indicating that language lateralization was generally affected by a left hippocampal sclerosis. Patients with left frontal lobe or temporal-lateral lesions displayed the same left lateralization of language-related activations as the control subjects. Thus, the hippocampus seems to play an important role in the establishment of language dominance. Possible underlying mechanisms are discussed.
Summary: Purpose: To determine whether language functional magnetic resonance imaging (fMRI) before epilepsy surgery can be similarly interpreted in patients with greatly different performance levels.
Methods: An fMRI paradigm using a semantic decision task with performance control and a perceptual control task was applied to 226 consecutive patients with drug‐resistant localization‐related epilepsy during their presurgical evaluations. The volume of activation and lateralization in an inferior frontal and a temporoparietal area was assessed in correlation with individual performance levels.
Results: We observed differential effects of task performance on the volume of activation in the inferior frontal and the temporoparietal region of interest, but performance measures did not correlate with the lateralization of activation.
Conclusions: fMRI, as applied here, in patients with a wide range of cognitive abilities, can be interpreted regarding language lateralization in a similar way.
2005
This paper investigates the driving forces behind informal sanctions in cooperation games and the extent to which theories of fairness and reciprocity capture these forces. We find that cooperators’ punishment is almost exclusively targeted toward the defec- tors, but the latter also impose a considerable amount of spiteful punishment on the cooperators. However, spiteful punishment vanishes if the punishers can no longer af- fect the payoff differences between themselves and the punished individual, whereas the cooperators even increase the resources devoted to punishment in this case. Our data also discriminate between different fairness principles. Fairness theories that are based on the assumption that players compare their own payoff to the group’s average or the group’s total payoff cannot explain the fact that cooperators target their punish- ment at the defectors. Fairness theories that assume that players aim to minimize payoff inequalities cannot explain the fact that cooperators punish defectors even if payoff in- equalities cannot be reduced. Therefore, retaliation, i.e., the desire to harm those who committed unfair acts, seems to be the most important motive behind fairness-driven informal sanctions.
This paper suggests a novel approach to program evaluation that allows identification of the causal effect of a training program on the likelihood of being invited to a job interview under weak assumptions, i.e., by measuring the program-effects by pre- and post-treatment data that are very close in time for the same individual.
We analyzed intracranial electroencephalographic (EEG) recordings from the medial temporal lobes of 12 epilepsy patients during a continuous word recognition paradigm, contrasting trials of correctly recognized repeated words (hits) and correctly identified new words (correct rejections). Using a wavelet-based analysis, we investigated how power changes and phase clustering in different frequency bands contribute to the averaged event-related potentials (ERPs). In addition, we analyzed the actual mean phases of the different oscillations. Our analyses yielded the following results: (1) power changes contributed significantly only to the late components of the ERPs (>400 ms) (2) earlier ERP components were produced by a stimulus-related broad-band phase and amplitude reset of ongoing oscillatory activity about 190 ms after stimulus onset that involved not only the theta band, but also covered alpha and lower beta band frequencies (3) phase and amplitude reset occurred during an epoch of increased phase entrainment over time that lasted for about two oscillation periods for all involved frequencies and was more pronounced for correct rejections than for hits. The broad-band phase and amplitude reset was observed for both hits and correct rejections, and therefore, did not appear to support a specific cognitive function, but rather to act as a general facilitating factor for the processes involved in this memory task. Further analyses of synchronization between oscillations and power changes in different frequency bands revealed a task-dependent modulation of gamma activity by the entrained theta cycle, a mechanism potentially related to memory encoding and retrieval in the rhinal cortex and hippocampus, respectively.
An essential, evolutionarily stable feature of brain function is the detection of animate entities, and one of the main cues to identify them is their movement. We developed a model of a simple interaction between two objects, in which an increase of the correlation between their movements varied the amount of interactivity and animacy observers attributed to them. Functional magnetic resonance imaging revealed that activation in the posterior superior temporal sulcus and gyrus (pSTS/pSTG) increased in relation to the degree of correlated motion between the two objects. This activation increase was not different when subjects performed an explicit or implicit task while observing these interacting objects. These data suggest that the pSTS and pSTG play a role in the automatic identification of animate entities, by responding directly to an objective movement characteristic inducing the percept of animacy, such as the amount of interactivity between two moving objects.
2004
We provide evidence that long-term relationships between trading parties emerge endogenously in the absence of third party enforcement of contracts and are associ- ated with a fundamental change in the nature of market interactions. Without third party enforcement, the vast majority of trades are initiated with private offers and the parties share the gains from trade equally. Low effort or bad quality is penalized by the termination of the relationship, wielding a powerful effect on contract enforcement. Successful long-term relations exhibit generous rent sharing and high effort (quality) from the very beginning of the relationship. In the absence of third-party enforcement, markets resemble a collection of bilateral trading islands rather than a competitive mar- ket. If contracts are third party enforceable, rent sharing and long-term relations are absent and the vast majority of trades are initiated with public offers. Most trades take place in one-shot transactions and the contracting parties are indifferent with regard to the identity of their trading partner.
A growing economic literature stresses the importance of relative comparisons, e.g., for savings and consumption or happiness. In this literature it is usually assumed that reference standards against which people compare themselves are exogenously given. In contrast, findings from social psychology suggest that people play an active role in determining their reference standards. We introduce a social comparison model where people choose their reference standards to serve motives of self-improvement and self-enhancement. The model predicts that reference standards increase in individuals’ abilities and that people thus tend to compare themselves to similar others. The results of a questionnaire study confirm the prediction.
Spatial memory deficits are core features of aging-related changes in cognitive abilities. The neural correlates of these deficits are largely unknown. In the present study, we investigated the neural underpinnings of age-related differences in spatial memory by functional MRI using a navigational memory task with route encoding and route recognition conditions. We investigated 20 healthy young (18-29 years old) and 20 healthy old adults (53-78 years old) in a random effects analysis. Old subjects showed slightly poorer performance than young subjects. Compared to the control condition, route encoding and route recognition showed activation of the dorsal and ventral visual processing streams and the frontal eye fields in both groups of subjects. Compared to old adults, young subjects showed during route encoding stronger activations in the dorsal and the ventral visual processing stream (supramarginal gyrus and posterior fusiform/parahippocampal areas). In addition, young subjects showed weaker anterior parahippocampal activity during route recognition compared to the old group. In contrast, old compared to young subjects showed less suppressed activity in the left perisylvian region and the anterior cingulate cortex during route encoding. Our findings suggest that age-related navigational memory deficits might be caused by less effective route encoding based on reduced posterior fusiform/parahippocampal and parietal functionality combined with diminished inhibition of perisylvian and anterior cingulate cortices correlated with less effective suppression of task-irrelevant information. In contrast, age differences in neural correlates of route recognition seem to be rather subtle. Old subjects might show a diminished familiarity signal during route recognition in the anterior parahippocampal region:
Previous functional imaging experiments in humans showed activation increases in the posterior superior temporal gyrus and sulcus during observation of geometrical shapes whose movements appear intentional or goal-directed. We modeled a chase scenario between two objects, in which the chasing object used different strategies to reach the target object: The chaser either followed the target's path or appeared to predict its end position. Activation in the superior temporal gyrus of human observers was greater when the chaser adopted a predict rather than a follow strategy. Attending to the chaser's strategy induced slightly greater activation in the left superior temporal gyrus than attending to the outcome of the chase. These data implicate the superior temporal gyrus in the identification of objects displaying complex goal-directed motion.
We suggest that certain experiences reported by patients with schizophrenia show that priority, consistency, and exclusivity are not sufficient for the experience of willing an action. Furthermore, we argue that even if priority, consistency, and exclusivity cause the experience of being the author of an action, this does not mean that conscious will is an illusion.
Navigation through familiar environments can rely upon distinct neural representations that are related to different memory systems with either the hippocampus or the caudate nucleus at their core. However, it is a fundamental question whether and how these systems interact during route recognition. To address this issue, we combined a functional neuroimaging approach with a naturally occurring, well-controlled human model of caudate nucleus dysfunction (i.e., preclinical and early-stage Huntington's disease). Our results reveal a noncompetitive interaction so that the hippocampus compensates for gradual caudate nucleus dysfunction with a gradual activity increase, maintaining normal behavior. Furthermore, we revealed an interaction between medial temporal and caudate activity in healthy subjects, which was adaptively modified in Huntington patients to allow compensatory hippocampal processing. Thus, the two memory systems contribute in a noncompetitive, cooperative manner to route recognition, which enables the hippocampus to compensate seamlessly for the functional degradation of the caudate nucleus.
2003
Over the last decades, there has been a steady increase in the use of experimental methods in economics. We discuss the advantages of experiments for labour economics in this paper. Control is the most important asset behind running experiments; no other empirical method allows a similarly tight control as do experiments. Moreover, experiments produce replicable evidence and permit the implementation of truly exogenous ceteris paribus changes. We also discuss frequent objections to experiments, such as a potential subject pool bias, the stake levels used in experiments, the number of observations as well as internal and external validity. We argue that although these objections are important, careful experimentation can circumvent them. While we think that lab and field experiments offer a very valuable tool, they should not be viewed as substitutes but as complements to more traditional methods of empirical economic analysis.
In this paper we experimentally study the effects of fairness, spite, and reputation formation on conflict. We show that fairness preferences are a potential source of conflict and that intentions play an important role in the perception of fairness. Further, we show that feelings of spite may affect the occurrence of conflict. Fi- nally, we study reputation formation as a possible source of conflict.We show that people invest in a reputation of being a tough bargainer. This does not automati- cally increase conflict, however. The reason is that through reputation, information about one’s opponent is much better than in anonymous bargaining.
2002
According to the standard economic perspective, criminal activities vary with the ‘price’ of crime, which depends on the severity of punishment and the detection probability. An alternative view claims that crime is also influenced by social interaction phenomena, such as ‘peer pressure’ or ‘neighbourhood effects’. Detecting social interaction in the field is fraught with difficulties, however. In this paper, we argue that given its extensive control possibilities, experiments are well suited to show the potential existence of social interaction effects. We present an experimental study where people can engage in ‘criminal’ activities. We find support for the importance of social interaction: On average subjects steal the more, the more others steal. This behaviour can be interpreted in terms of reciprocity.
During the last two decades economists have made much progress in understanding incentives, contracts and organizations. Yet, they constrained their attention to a very narrow and empirically questionable view of human motivation. The purpose of this paper is to show that this narrow view of human motivation may severely limit understanding the determinants and effects of incentives. Economists may fail to understand the levels and the changes in behaviour if they neglect motives like the desire to reciprocate or the desire to avoid social disapproval. We show that monetary incentives may backfire and reduce the performance of agents or their compliance with rules. In addition, these motives may generate very powerful incentives themselves.
Recent evidence highlights the importance of social norms in many economic relations. However, many of these relationships are long term and provide repeated game incentives for performance. We experimentally investigate interaction effects of reciprocity and repeated game incentives in two treatments (one-shot and repeated) of a gift-exchange game. In both treatments we observe reciprocity, which is strengthened in the repeated game. A detailed analysis shows that, in the repeated game, some subjects imitate reciprocity. Thus, reciprocity and repeated game incentives reinforce each other. Observed behaviour is robust against experience. We conclude that long-term interaction is a "reciprocity-compatible'' contract enforcement device.
2001
Two types of theoretic approaches have been developed to model fair behavior. According to the "equity approach" fairness is solely driven by distributional concerns. Opposed to this consequentialistic perspective, the "reciprocity approach" stresses the importance of intentions. We discuss experimental evidence that demonstrates that in fact both intentions and distributional consequences matter. In this paper, we present a formal model of reciprocity that captures both, outcomes and intentions.
Cannabinoid CB1 receptors occur as presynaptic receptors producing inhibition of neurotransmitter release. To elucidate their physiological role, experiments on tissues from CB1 receptor knockout mice would be helpful. We studied whether CB1 receptor-mediated inhibition of acetylcholine release is detectable in the brain of NMRI mice and of CD-1 and C57BL/6J mice (the latter two strains representing the wild-type strains of the two CB1 receptor knockout mouse models). Brain slices preincubated with [3H]choline were superfused and tritium overflow was evoked electrically (3 Hz) or by introduction of Ca2+ into Ca2+-free K+-rich medium (35 mM) containing tetrodotoxin. The electrically evoked tritium overflow from NMRI mouse hippocampal slices was inhibited (maximally by 60%) by the cannabinoid receptor agonists CP-55,940 and WIN 55,212-2 but not affected by WIN 55,212-3 (the in-active enantiomer of WIN 55,212-2; pEC50=7.9, 7.4 and < 5.5). The concentration-response curve of WIN 55,212-2 was shifted to the right by the CB1 receptor antagonist SR 141716 (apparent pA2=8.6). Compared to hippocampal slices from NMRI mice, WIN 55,212-2 1 μM inhibited the electrically evoked overflow (1) from cortical slices from NMRI mice to a lesser extent and from striatal slices not at all, (2) from hippocampal slices from CD-1 and C57BL/6J mice to an identical extent and (3) from hippocampal slices from Sprague-Dawley rats to at least the same extent. SR 141716 0.32 μM abolished the effect of WIN 55,212-2 1 μM in hippocampal slices from NMRI, CD-1 and C57BL/6J mice and in cortical slices from NMRI mice. The electrically evoked tritium overflow from NMRI mouse hippocampal slices was also inhibited by the muscarinic receptor agonist oxotremorine (maximum effect of 85%; pEC50=6.5) and this effect was antagonized by the muscarinic receptor antagonist AF-DX 384 (apparent pA2=8.3). The Ca2+-evoked tritium overflow from NMRI mouse hippocampal slices was inhibited by WIN 55,212-2 in a manner sensitive to SR 141716. In conclusion, the cholinergic axon terminals; of the NMRI mouse hippocampus are endowed with presynaptic CB1 receptors. Such receptors are also detectable in the hippocampus of CD-1 and C57BL/6J mice. The maximum extent of the CB1 receptor-mediated inhibition of acetylcholine release is lower than the maximum effect mediated via the autoreceptor.
We examined whether acetylcholine release in the hippocampus and striatum and noradrenaline release in the hippocampus is altered in CB1 receptor-deficient mice. The electrically evoked tritium overflow from hippocampal slices preincubated with [3H]-choline was increased by about 100% in CB1-/- compared to CB1+/+ mice whereas the electrically evoked tritium overflow from striatal slices preincubated with [3H]-choline and from hippocampal slices preincubated with [3H]-noradrenaline did not differ. The cannabinoid receptor agonist, WIN 55,212-2, inhibited, and the CB1 receptor antagonist, SR 141716, facilitated, the evoked tritium overflow from hippocampal slices (preincubated with [3H]-choline) from CB1+/+ as opposed to CB1-/- mice. Both drugs did not affect the evoked tritium overflow from striatal slices (preincubated with [3H]-choline) and from hippocampal slices (preincubated with [3H]-noradrenaline) from CB1+/+ and CB1-/- mice. The selective increase in acetylcholine release in CB1-/- mice may indicate that the presynaptic CB1 receptors on the cholinergic neurones of the mouse hippocampus are tonically activated and/or constitutively active in vivo.
The modulation of dopamine release from the guinea-pig retina was studied using maximally effective concentrations of 10 agonists acting on Gi-, Gs- or Gq-protein-coupled receptors (PCRs). Retinal discs were preincubated with [3H]noradrenaline and superfused; tritium overflow was evoked electrically. The following compounds acting on Gi-PCRs reduced the tritium overflow, which represents quasi-physiological dopamine release under the experimental conditions of our study: the dopamine and α2-adrenoceptor agonist B-HT 920 by 95%, the muscarinic agonist oxotremorine by 96%, melatonin by 94%, the cannabinoid agonist WIN 55,212-2 by 71% and histamine by 66%. Tritium overflow was not affected by serotonin or by agonists acting on Gs-PCRs (ACTH1-24and the β-adrenoceptor agonist procaterol) and Gq-PCRs (angiotensin II and bradykinin). The effects of B-HT 920, oxotremorine and melatonin were studied in more detail using appropriate antagonists. The inhibitory effect of a submaximally active concentration of B-HT 920 was counteracted by the dopamine D2/3antagonist haloperidol but not affected by the α2-adrenoceptor antagonist phentolamine. The muscarinic antagonist atropine shifted to the right the concentration-response curve of oxotremorine (pA28.7) and the melatonin MT2antagonist 4-P-PDOT produced a rightward shift of the concentration-response curve of melatonin (pA210.6). Melatonin was also studied in superfused brain slices (from the guinea-pig) preincubated with [3H]noradrenaline. The electrically evoked tritium overflow in cerebrocortical, hippocampal and hypothalamic slices (representing quasi-physiological noradrenaline release) and in striatal slices (representing quasi-physiological dopamine release) was not affected by melatonin at a concentration that causes the maximum effect in retinal discs. In conclusion, dopamine release in the guinea-pig retina is inhibited via Gi-PCRs including dopamine (D2/3), muscarinic and melatonin (MT2) receptors but not affected via any of the Gs- or Gq-PCRs under study. Unlike in the retina, melatonin fails to inhibit monoamine release in four brain regions of the guinea-pig.
1. Dopamine release in the retina is subject to modulation via autoreceptors, which belong to the D2 receptor family (encompassing the D2, D3 and D4 receptors). The aim of the present study was to determine the receptor subtype (D2 vs D3) involved in the inhibition of dopamine release in guinea-pig retinal discs, using established (haloperidol, (S)-nafadotride) and novel dopamine receptor antagonists (ST-148, ST-198). 2. hD2L and hD3 receptors were expressed in CHO cells and the pKi values determined in binding studies with [125I]-iodosulpride were: haloperidol 9.22 vs 8.54; ST-148 7.85 vs 6.60; (S)-nafadotride 8.52 vs 9.51; ST-198 6.14 vs 7.92. 3. The electrically evoked tritium overflow from retinal discs preincubated with [3H]-noradrenaline (which represents quasi-physiological dopamine release) was inhibited by the dopamine receptor agonists B-HT 920 (talipexole) and quinpirole (maximally by 82 and 71%; pEC50 5.80 and 5.83). The concentration-response curves of these agonists were shifted to the right by haloperidol (apparent pA2 8.69 and 8.23) and ST-148 (7.52 and 7.66). (S)-Nafadotride 0.01 μM and ST-198 0.32 μM did not affect the concentration-response curve of B-HT 920. 4. The dopamine autoreceptor in the guinea-pig retina can be classified as a D2 receptor. ST-148 and ST-198 show an improved selectivity for D2 and D3 receptors when compared to haloperidol and (S)-nafadotride, respectively.
1999
Important features of labor relations are that contracts are incomplete, that workers and firms very often interact repeatedly and that there are opportunities for social exchange. To assess the relative importance of these features, we experimentally examine behavior in a game with incomplete contracts. Our main results are that mere repeated interaction with the same player increased effort levels as compared to one-shot interactions. Social approval incentives were not very important in our experiments. Reciprocal behavior clearly was the dominant pattern. Most of it was intrinsic reciprocity, i.e., neither repeated play nor approval incentives influenced the extent of reciprocity very much. We also show that there exist treatment-dependent equity considerations.
Do employers and workers underbid prevailing wages if there is unemployment? Do employers take advantage of workers’ underbidding by lowering wages? We hypothesize that under conditions of incomplete labor contracts wage levels may positively affect workers’ propensity to cooperate. This, in turn, may prevent firms from underbidding or accepting the underbidding of workers. To get controlled evidence we conducted several experimental double auction markets. Double auctions are well known for their striking competitive properties. Our data show, however, the following regularities: (i) Workers’ underbidding is very frequent but employers refuse to accept workers’ low wage offers in markets with incomplete labor contracts. However, in the presence of complete labor contracts employers accept and actively enforce wages close to the competitive level. (ii) Workers’ effort is positively related to the wage level. Therefore, wage cutting is costly for the employer if workers have discretion over their effort level. This holds true even in the presence of explicit performance incentives. In markets with incomplete contracts firms’ high wage strategy increases the gains from trade and renders both workers and firms better off. (This abstract was borrowed from another version of this item.)